node fixes, updates

13 files changed, 1686 insertions, 1617 deletions

diff --git a/node_modules/source-map/lib/array-set.js b/node_modules/source-map/lib/array-set.js
index fbd5c81c..40171b9a 100644
--- a/node_modules/source-map/lib/array-set.js
+++ b/node_modules/source-map/lib/array-set.js
@@ -5,117 +5,96 @@
  * http://opensource.org/licenses/BSD-3-Clause
  */
 
-var util = require('./util');
-var has = Object.prototype.hasOwnProperty;
-var hasNativeMap = typeof Map !== "undefined";
-
 /**
  * A data structure which is a combination of an array and a set. Adding a new
  * member is O(1), testing for membership is O(1), and finding the index of an
  * element is O(1). Removing elements from the set is not supported. Only
  * strings are supported for membership.
  */
-function ArraySet() {
-  this._array = [];
-  this._set = hasNativeMap ? new Map() : Object.create(null);
-}
-
-/**
- * Static method for creating ArraySet instances from an existing array.
- */
-ArraySet.fromArray = function ArraySet_fromArray(aArray, aAllowDuplicates) {
-  var set = new ArraySet();
-  for (var i = 0, len = aArray.length; i < len; i++) {
-    set.add(aArray[i], aAllowDuplicates);
+class ArraySet {
+  constructor() {
+    this._array = [];
+    this._set = new Map();
   }
-  return set;
-};
 
-/**
- * Return how many unique items are in this ArraySet. If duplicates have been
- * added, than those do not count towards the size.
- *
- * @returns Number
- */
-ArraySet.prototype.size = function ArraySet_size() {
-  return hasNativeMap ? this._set.size : Object.getOwnPropertyNames(this._set).length;
-};
+  /**
+   * Static method for creating ArraySet instances from an existing array.
+   */
+  static fromArray(aArray, aAllowDuplicates) {
+    const set = new ArraySet();
+    for (let i = 0, len = aArray.length; i < len; i++) {
+      set.add(aArray[i], aAllowDuplicates);
+    }
+    return set;
+  }
 
-/**
- * Add the given string to this set.
- *
- * @param String aStr
- */
-ArraySet.prototype.add = function ArraySet_add(aStr, aAllowDuplicates) {
-  var sStr = hasNativeMap ? aStr : util.toSetString(aStr);
-  var isDuplicate = hasNativeMap ? this.has(aStr) : has.call(this._set, sStr);
-  var idx = this._array.length;
-  if (!isDuplicate || aAllowDuplicates) {
-    this._array.push(aStr);
+  /**
+   * Return how many unique items are in this ArraySet. If duplicates have been
+   * added, than those do not count towards the size.
+   *
+   * @returns Number
+   */
+  size() {
+    return this._set.size;
   }
-  if (!isDuplicate) {
-    if (hasNativeMap) {
+
+  /**
+   * Add the given string to this set.
+   *
+   * @param String aStr
+   */
+  add(aStr, aAllowDuplicates) {
+    const isDuplicate = this.has(aStr);
+    const idx = this._array.length;
+    if (!isDuplicate || aAllowDuplicates) {
+      this._array.push(aStr);
+    }
+    if (!isDuplicate) {
       this._set.set(aStr, idx);
-    } else {
-      this._set[sStr] = idx;
     }
   }
-};
 
-/**
- * Is the given string a member of this set?
- *
- * @param String aStr
- */
-ArraySet.prototype.has = function ArraySet_has(aStr) {
-  if (hasNativeMap) {
-    return this._set.has(aStr);
-  } else {
-    var sStr = util.toSetString(aStr);
-    return has.call(this._set, sStr);
+  /**
+   * Is the given string a member of this set?
+   *
+   * @param String aStr
+   */
+  has(aStr) {
+      return this._set.has(aStr);
   }
-};
 
-/**
- * What is the index of the given string in the array?
- *
- * @param String aStr
- */
-ArraySet.prototype.indexOf = function ArraySet_indexOf(aStr) {
-  if (hasNativeMap) {
-    var idx = this._set.get(aStr);
+  /**
+   * What is the index of the given string in the array?
+   *
+   * @param String aStr
+   */
+  indexOf(aStr) {
+    const idx = this._set.get(aStr);
     if (idx >= 0) {
         return idx;
     }
-  } else {
-    var sStr = util.toSetString(aStr);
-    if (has.call(this._set, sStr)) {
-      return this._set[sStr];
-    }
+    throw new Error('"' + aStr + '" is not in the set.');
   }
 
-  throw new Error('"' + aStr + '" is not in the set.');
-};
-
-/**
- * What is the element at the given index?
- *
- * @param Number aIdx
- */
-ArraySet.prototype.at = function ArraySet_at(aIdx) {
-  if (aIdx >= 0 && aIdx < this._array.length) {
-    return this._array[aIdx];
+  /**
+   * What is the element at the given index?
+   *
+   * @param Number aIdx
+   */
+  at(aIdx) {
+    if (aIdx >= 0 && aIdx < this._array.length) {
+      return this._array[aIdx];
+    }
+    throw new Error("No element indexed by " + aIdx);
   }
-  throw new Error('No element indexed by ' + aIdx);
-};
-
-/**
- * Returns the array representation of this set (which has the proper indices
- * indicated by indexOf). Note that this is a copy of the internal array used
- * for storing the members so that no one can mess with internal state.
- */
-ArraySet.prototype.toArray = function ArraySet_toArray() {
-  return this._array.slice();
-};
 
+  /**
+   * Returns the array representation of this set (which has the proper indices
+   * indicated by indexOf). Note that this is a copy of the internal array used
+   * for storing the members so that no one can mess with internal state.
+   */
+  toArray() {
+    return this._array.slice();
+  }
+}
 exports.ArraySet = ArraySet;
diff --git a/node_modules/source-map/lib/base64-vlq.js b/node_modules/source-map/lib/base64-vlq.js
index 612b4040..fc1049c8 100644
--- a/node_modules/source-map/lib/base64-vlq.js
+++ b/node_modules/source-map/lib/base64-vlq.js
@@ -35,7 +35,7 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-var base64 = require('./base64');
+const base64 = require("./base64");
 
 // A single base 64 digit can contain 6 bits of data. For the base 64 variable
 // length quantities we use in the source map spec, the first bit is the sign,
@@ -49,16 +49,16 @@ var base64 = require('./base64');
 //   V    V
 //   101011
 
-var VLQ_BASE_SHIFT = 5;
+const VLQ_BASE_SHIFT = 5;
 
 // binary: 100000
-var VLQ_BASE = 1 << VLQ_BASE_SHIFT;
+const VLQ_BASE = 1 << VLQ_BASE_SHIFT;
 
 // binary: 011111
-var VLQ_BASE_MASK = VLQ_BASE - 1;
+const VLQ_BASE_MASK = VLQ_BASE - 1;
 
 // binary: 100000
-var VLQ_CONTINUATION_BIT = VLQ_BASE;
+const VLQ_CONTINUATION_BIT = VLQ_BASE;
 
 /**
  * Converts from a two-complement value to a value where the sign bit is
@@ -78,9 +78,10 @@ function toVLQSigned(aValue) {
  *   2 (10 binary) becomes 1, 3 (11 binary) becomes -1
  *   4 (100 binary) becomes 2, 5 (101 binary) becomes -2
  */
+// eslint-disable-next-line no-unused-vars
 function fromVLQSigned(aValue) {
-  var isNegative = (aValue & 1) === 1;
-  var shifted = aValue >> 1;
+  const isNegative = (aValue & 1) === 1;
+  const shifted = aValue >> 1;
   return isNegative
     ? -shifted
     : shifted;
@@ -90,10 +91,10 @@ function fromVLQSigned(aValue) {
  * Returns the base 64 VLQ encoded value.
  */
 exports.encode = function base64VLQ_encode(aValue) {
-  var encoded = "";
-  var digit;
+  let encoded = "";
+  let digit;
 
-  var vlq = toVLQSigned(aValue);
+  let vlq = toVLQSigned(aValue);
 
   do {
     digit = vlq & VLQ_BASE_MASK;
@@ -108,33 +109,3 @@ exports.encode = function base64VLQ_encode(aValue) {
 
   return encoded;
 };
-
-/**
- * Decodes the next base 64 VLQ value from the given string and returns the
- * value and the rest of the string via the out parameter.
- */
-exports.decode = function base64VLQ_decode(aStr, aIndex, aOutParam) {
-  var strLen = aStr.length;
-  var result = 0;
-  var shift = 0;
-  var continuation, digit;
-
-  do {
-    if (aIndex >= strLen) {
-      throw new Error("Expected more digits in base 64 VLQ value.");
-    }
-
-    digit = base64.decode(aStr.charCodeAt(aIndex++));
-    if (digit === -1) {
-      throw new Error("Invalid base64 digit: " + aStr.charAt(aIndex - 1));
-    }
-
-    continuation = !!(digit & VLQ_CONTINUATION_BIT);
-    digit &= VLQ_BASE_MASK;
-    result = result + (digit << shift);
-    shift += VLQ_BASE_SHIFT;
-  } while (continuation);
-
-  aOutParam.value = fromVLQSigned(result);
-  aOutParam.rest = aIndex;
-};
diff --git a/node_modules/source-map/lib/base64.js b/node_modules/source-map/lib/base64.js
index 8aa86b30..b9ca3199 100644
--- a/node_modules/source-map/lib/base64.js
+++ b/node_modules/source-map/lib/base64.js
@@ -5,63 +5,14 @@
  * http://opensource.org/licenses/BSD-3-Clause
  */
 
-var intToCharMap = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/'.split('');
+const intToCharMap = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".split("");
 
 /**
  * Encode an integer in the range of 0 to 63 to a single base 64 digit.
  */
-exports.encode = function (number) {
+exports.encode = function(number) {
   if (0 <= number && number < intToCharMap.length) {
     return intToCharMap[number];
   }
   throw new TypeError("Must be between 0 and 63: " + number);
 };
-
-/**
- * Decode a single base 64 character code digit to an integer. Returns -1 on
- * failure.
- */
-exports.decode = function (charCode) {
-  var bigA = 65;     // 'A'
-  var bigZ = 90;     // 'Z'
-
-  var littleA = 97;  // 'a'
-  var littleZ = 122; // 'z'
-
-  var zero = 48;     // '0'
-  var nine = 57;     // '9'
-
-  var plus = 43;     // '+'
-  var slash = 47;    // '/'
-
-  var littleOffset = 26;
-  var numberOffset = 52;
-
-  // 0 - 25: ABCDEFGHIJKLMNOPQRSTUVWXYZ
-  if (bigA <= charCode && charCode <= bigZ) {
-    return (charCode - bigA);
-  }
-
-  // 26 - 51: abcdefghijklmnopqrstuvwxyz
-  if (littleA <= charCode && charCode <= littleZ) {
-    return (charCode - littleA + littleOffset);
-  }
-
-  // 52 - 61: 0123456789
-  if (zero <= charCode && charCode <= nine) {
-    return (charCode - zero + numberOffset);
-  }
-
-  // 62: +
-  if (charCode == plus) {
-    return 62;
-  }
-
-  // 63: /
-  if (charCode == slash) {
-    return 63;
-  }
-
-  // Invalid base64 digit.
-  return -1;
-};
diff --git a/node_modules/source-map/lib/binary-search.js b/node_modules/source-map/lib/binary-search.js
index 010ac941..d6f898ea 100644
--- a/node_modules/source-map/lib/binary-search.js
+++ b/node_modules/source-map/lib/binary-search.js
@@ -31,13 +31,12 @@ function recursiveSearch(aLow, aHigh, aNeedle, aHaystack, aCompare, aBias) {
   //
   //   3. We did not find the exact element, and there is no next-closest
   //      element than the one we are searching for, so we return -1.
-  var mid = Math.floor((aHigh - aLow) / 2) + aLow;
-  var cmp = aCompare(aNeedle, aHaystack[mid], true);
+  const mid = Math.floor((aHigh - aLow) / 2) + aLow;
+  const cmp = aCompare(aNeedle, aHaystack[mid], true);
   if (cmp === 0) {
     // Found the element we are looking for.
     return mid;
-  }
-  else if (cmp > 0) {
+  } else if (cmp > 0) {
     // Our needle is greater than aHaystack[mid].
     if (aHigh - mid > 1) {
       // The element is in the upper half.
@@ -48,24 +47,21 @@ function recursiveSearch(aLow, aHigh, aNeedle, aHaystack, aCompare, aBias) {
     // we are in termination case (3) or (2) and return the appropriate thing.
     if (aBias == exports.LEAST_UPPER_BOUND) {
       return aHigh < aHaystack.length ? aHigh : -1;
-    } else {
-      return mid;
     }
+    return mid;
   }
-  else {
-    // Our needle is less than aHaystack[mid].
-    if (mid - aLow > 1) {
-      // The element is in the lower half.
-      return recursiveSearch(aLow, mid, aNeedle, aHaystack, aCompare, aBias);
-    }
 
-    // we are in termination case (3) or (2) and return the appropriate thing.
-    if (aBias == exports.LEAST_UPPER_BOUND) {
-      return mid;
-    } else {
-      return aLow < 0 ? -1 : aLow;
-    }
+  // Our needle is less than aHaystack[mid].
+  if (mid - aLow > 1) {
+    // The element is in the lower half.
+    return recursiveSearch(aLow, mid, aNeedle, aHaystack, aCompare, aBias);
+  }
+
+  // we are in termination case (3) or (2) and return the appropriate thing.
+  if (aBias == exports.LEAST_UPPER_BOUND) {
+    return mid;
   }
+  return aLow < 0 ? -1 : aLow;
 }
 
 /**
@@ -91,7 +87,7 @@ exports.search = function search(aNeedle, aHaystack, aCompare, aBias) {
     return -1;
   }
 
-  var index = recursiveSearch(-1, aHaystack.length, aNeedle, aHaystack,
+  let index = recursiveSearch(-1, aHaystack.length, aNeedle, aHaystack,
                               aCompare, aBias || exports.GREATEST_LOWER_BOUND);
   if (index < 0) {
     return -1;
diff --git a/node_modules/source-map/lib/mapping-list.js b/node_modules/source-map/lib/mapping-list.js
index 06d1274a..70568610 100644
--- a/node_modules/source-map/lib/mapping-list.js
+++ b/node_modules/source-map/lib/mapping-list.js
@@ -5,7 +5,7 @@
  * http://opensource.org/licenses/BSD-3-Clause
  */
 
-var util = require('./util');
+const util = require("./util");
 
 /**
  * Determine whether mappingB is after mappingA with respect to generated
@@ -13,67 +13,68 @@ var util = require('./util');
  */
 function generatedPositionAfter(mappingA, mappingB) {
   // Optimized for most common case
-  var lineA = mappingA.generatedLine;
-  var lineB = mappingB.generatedLine;
-  var columnA = mappingA.generatedColumn;
-  var columnB = mappingB.generatedColumn;
+  const lineA = mappingA.generatedLine;
+  const lineB = mappingB.generatedLine;
+  const columnA = mappingA.generatedColumn;
+  const columnB = mappingB.generatedColumn;
   return lineB > lineA || lineB == lineA && columnB >= columnA ||
          util.compareByGeneratedPositionsInflated(mappingA, mappingB) <= 0;
 }
 
 /**
  * A data structure to provide a sorted view of accumulated mappings in a
- * performance conscious manner. It trades a neglibable overhead in general
+ * performance conscious manner. It trades a negligible overhead in general
  * case for a large speedup in case of mappings being added in order.
  */
-function MappingList() {
-  this._array = [];
-  this._sorted = true;
-  // Serves as infimum
-  this._last = {generatedLine: -1, generatedColumn: 0};
-}
+class MappingList {
+  constructor() {
+    this._array = [];
+    this._sorted = true;
+    // Serves as infimum
+    this._last = {generatedLine: -1, generatedColumn: 0};
+  }
 
-/**
- * Iterate through internal items. This method takes the same arguments that
- * `Array.prototype.forEach` takes.
- *
- * NOTE: The order of the mappings is NOT guaranteed.
- */
-MappingList.prototype.unsortedForEach =
-  function MappingList_forEach(aCallback, aThisArg) {
+  /**
+   * Iterate through internal items. This method takes the same arguments that
+   * `Array.prototype.forEach` takes.
+   *
+   * NOTE: The order of the mappings is NOT guaranteed.
+   */
+  unsortedForEach(aCallback, aThisArg) {
     this._array.forEach(aCallback, aThisArg);
-  };
+  }
 
-/**
- * Add the given source mapping.
- *
- * @param Object aMapping
- */
-MappingList.prototype.add = function MappingList_add(aMapping) {
-  if (generatedPositionAfter(this._last, aMapping)) {
-    this._last = aMapping;
-    this._array.push(aMapping);
-  } else {
-    this._sorted = false;
-    this._array.push(aMapping);
+  /**
+   * Add the given source mapping.
+   *
+   * @param Object aMapping
+   */
+  add(aMapping) {
+    if (generatedPositionAfter(this._last, aMapping)) {
+      this._last = aMapping;
+      this._array.push(aMapping);
+    } else {
+      this._sorted = false;
+      this._array.push(aMapping);
+    }
   }
-};
 
-/**
- * Returns the flat, sorted array of mappings. The mappings are sorted by
- * generated position.
- *
- * WARNING: This method returns internal data without copying, for
- * performance. The return value must NOT be mutated, and should be treated as
- * an immutable borrow. If you want to take ownership, you must make your own
- * copy.
- */
-MappingList.prototype.toArray = function MappingList_toArray() {
-  if (!this._sorted) {
-    this._array.sort(util.compareByGeneratedPositionsInflated);
-    this._sorted = true;
+  /**
+   * Returns the flat, sorted array of mappings. The mappings are sorted by
+   * generated position.
+   *
+   * WARNING: This method returns internal data without copying, for
+   * performance. The return value must NOT be mutated, and should be treated as
+   * an immutable borrow. If you want to take ownership, you must make your own
+   * copy.
+   */
+  toArray() {
+    if (!this._sorted) {
+      this._array.sort(util.compareByGeneratedPositionsInflated);
+      this._sorted = true;
+    }
+    return this._array;
   }
-  return this._array;
-};
+}
 
 exports.MappingList = MappingList;
diff --git a/node_modules/source-map/lib/mappings.wasm b/node_modules/source-map/lib/mappings.wasm
new file mode 100644
index 00000000..35153707
--- /dev/null
+++ b/node_modules/source-map/lib/mappings.wasm
diff --git a/node_modules/source-map/lib/quick-sort.js b/node_modules/source-map/lib/quick-sort.js
deleted file mode 100644
index 6a7caadb..00000000
--- a/node_modules/source-map/lib/quick-sort.js
+++ /dev/null
@@ -1,114 +0,0 @@
-/* -*- Mode: js; js-indent-level: 2; -*- */
-/*
- * Copyright 2011 Mozilla Foundation and contributors
- * Licensed under the New BSD license. See LICENSE or:
- * http://opensource.org/licenses/BSD-3-Clause
- */
-
-// It turns out that some (most?) JavaScript engines don't self-host
-// `Array.prototype.sort`. This makes sense because C++ will likely remain
-// faster than JS when doing raw CPU-intensive sorting. However, when using a
-// custom comparator function, calling back and forth between the VM's C++ and
-// JIT'd JS is rather slow *and* loses JIT type information, resulting in
-// worse generated code for the comparator function than would be optimal. In
-// fact, when sorting with a comparator, these costs outweigh the benefits of
-// sorting in C++. By using our own JS-implemented Quick Sort (below), we get
-// a ~3500ms mean speed-up in `bench/bench.html`.
-
-/**
- * Swap the elements indexed by `x` and `y` in the array `ary`.
- *
- * @param {Array} ary
- *        The array.
- * @param {Number} x
- *        The index of the first item.
- * @param {Number} y
- *        The index of the second item.
- */
-function swap(ary, x, y) {
-  var temp = ary[x];
-  ary[x] = ary[y];
-  ary[y] = temp;
-}
-
-/**
- * Returns a random integer within the range `low .. high` inclusive.
- *
- * @param {Number} low
- *        The lower bound on the range.
- * @param {Number} high
- *        The upper bound on the range.
- */
-function randomIntInRange(low, high) {
-  return Math.round(low + (Math.random() * (high - low)));
-}
-
-/**
- * The Quick Sort algorithm.
- *
- * @param {Array} ary
- *        An array to sort.
- * @param {function} comparator
- *        Function to use to compare two items.
- * @param {Number} p
- *        Start index of the array
- * @param {Number} r
- *        End index of the array
- */
-function doQuickSort(ary, comparator, p, r) {
-  // If our lower bound is less than our upper bound, we (1) partition the
-  // array into two pieces and (2) recurse on each half. If it is not, this is
-  // the empty array and our base case.
-
-  if (p < r) {
-    // (1) Partitioning.
-    //
-    // The partitioning chooses a pivot between `p` and `r` and moves all
-    // elements that are less than or equal to the pivot to the before it, and
-    // all the elements that are greater than it after it. The effect is that
-    // once partition is done, the pivot is in the exact place it will be when
-    // the array is put in sorted order, and it will not need to be moved
-    // again. This runs in O(n) time.
-
-    // Always choose a random pivot so that an input array which is reverse
-    // sorted does not cause O(n^2) running time.
-    var pivotIndex = randomIntInRange(p, r);
-    var i = p - 1;
-
-    swap(ary, pivotIndex, r);
-    var pivot = ary[r];
-
-    // Immediately after `j` is incremented in this loop, the following hold
-    // true:
-    //
-    //   * Every element in `ary[p .. i]` is less than or equal to the pivot.
-    //
-    //   * Every element in `ary[i+1 .. j-1]` is greater than the pivot.
-    for (var j = p; j < r; j++) {
-      if (comparator(ary[j], pivot) <= 0) {
-        i += 1;
-        swap(ary, i, j);
-      }
-    }
-
-    swap(ary, i + 1, j);
-    var q = i + 1;
-
-    // (2) Recurse on each half.
-
-    doQuickSort(ary, comparator, p, q - 1);
-    doQuickSort(ary, comparator, q + 1, r);
-  }
-}
-
-/**
- * Sort the given array in-place with the given comparator function.
- *
- * @param {Array} ary
- *        An array to sort.
- * @param {function} comparator
- *        Function to use to compare two items.
- */
-exports.quickSort = function (ary, comparator) {
-  doQuickSort(ary, comparator, 0, ary.length - 1);
-};
diff --git a/node_modules/source-map/lib/read-wasm.js b/node_modules/source-map/lib/read-wasm.js
new file mode 100644
index 00000000..e81c1772
--- /dev/null
+++ b/node_modules/source-map/lib/read-wasm.js
@@ -0,0 +1,49 @@
+/* Determine browser vs node environment by testing the default top level context. Solution courtesy of: https://stackoverflow.com/questions/17575790/environment-detection-node-js-or-browser */
+const isBrowserEnvironment = (function() {
+    // eslint-disable-next-line no-undef
+    return (typeof window !== "undefined") && (this === window);
+}).call();
+
+if (isBrowserEnvironment) {
+  // Web version of reading a wasm file into an array buffer.
+
+  let mappingsWasm = null;
+
+  module.exports = function readWasm() {
+    if (typeof mappingsWasm === "string") {
+      return fetch(mappingsWasm)
+        .then(response => response.arrayBuffer());
+    }
+    if (mappingsWasm instanceof ArrayBuffer) {
+      return Promise.resolve(mappingsWasm);
+    }
+    throw new Error("You must provide the string URL or ArrayBuffer contents " +
+                    "of lib/mappings.wasm by calling " +
+                    "SourceMapConsumer.initialize({ 'lib/mappings.wasm': ... }) " +
+                    "before using SourceMapConsumer");
+  };
+
+  module.exports.initialize = input => mappingsWasm = input;
+} else {
+  // Node version of reading a wasm file into an array buffer.
+  const fs = require("fs");
+  const path = require("path");
+
+  module.exports = function readWasm() {
+    return new Promise((resolve, reject) => {
+      const wasmPath = path.join(__dirname, "mappings.wasm");
+      fs.readFile(wasmPath, null, (error, data) => {
+        if (error) {
+          reject(error);
+          return;
+        }
+
+        resolve(data.buffer);
+      });
+    });
+  };
+
+  module.exports.initialize = _ => {
+    console.debug("SourceMapConsumer.initialize is a no-op when running in node.js");
+  };
+}
diff --git a/node_modules/source-map/lib/source-map-consumer.js b/node_modules/source-map/lib/source-map-consumer.js
index 7b99d1da..9aaf92f5 100644
--- a/node_modules/source-map/lib/source-map-consumer.js
+++ b/node_modules/source-map/lib/source-map-consumer.js
@@ -5,250 +5,144 @@
  * http://opensource.org/licenses/BSD-3-Clause
  */
 
-var util = require('./util');
-var binarySearch = require('./binary-search');
-var ArraySet = require('./array-set').ArraySet;
-var base64VLQ = require('./base64-vlq');
-var quickSort = require('./quick-sort').quickSort;
-
-function SourceMapConsumer(aSourceMap, aSourceMapURL) {
-  var sourceMap = aSourceMap;
-  if (typeof aSourceMap === 'string') {
-    sourceMap = util.parseSourceMapInput(aSourceMap);
-  }
+const util = require("./util");
+const binarySearch = require("./binary-search");
+const ArraySet = require("./array-set").ArraySet;
+const base64VLQ = require("./base64-vlq"); // eslint-disable-line no-unused-vars
+const readWasm = require("../lib/read-wasm");
+const wasm = require("./wasm");
+
+const INTERNAL = Symbol("smcInternal");
+
+class SourceMapConsumer {
+  constructor(aSourceMap, aSourceMapURL) {
+    // If the constructor was called by super(), just return Promise<this>.
+    // Yes, this is a hack to retain the pre-existing API of the base-class
+    // constructor also being an async factory function.
+    if (aSourceMap == INTERNAL) {
+      return Promise.resolve(this);
+    }
 
-  return sourceMap.sections != null
-    ? new IndexedSourceMapConsumer(sourceMap, aSourceMapURL)
-    : new BasicSourceMapConsumer(sourceMap, aSourceMapURL);
-}
+    return _factory(aSourceMap, aSourceMapURL);
+  }
 
-SourceMapConsumer.fromSourceMap = function(aSourceMap, aSourceMapURL) {
-  return BasicSourceMapConsumer.fromSourceMap(aSourceMap, aSourceMapURL);
-}
+  static initialize(opts) {
+    readWasm.initialize(opts["lib/mappings.wasm"]);
+  }
 
-/**
- * The version of the source mapping spec that we are consuming.
- */
-SourceMapConsumer.prototype._version = 3;
+  static fromSourceMap(aSourceMap, aSourceMapURL) {
+    return _factoryBSM(aSourceMap, aSourceMapURL);
+  }
 
-// `__generatedMappings` and `__originalMappings` are arrays that hold the
-// parsed mapping coordinates from the source map's "mappings" attribute. They
-// are lazily instantiated, accessed via the `_generatedMappings` and
-// `_originalMappings` getters respectively, and we only parse the mappings
-// and create these arrays once queried for a source location. We jump through
-// these hoops because there can be many thousands of mappings, and parsing
-// them is expensive, so we only want to do it if we must.
-//
-// Each object in the arrays is of the form:
-//
-//     {
-//       generatedLine: The line number in the generated code,
-//       generatedColumn: The column number in the generated code,
-//       source: The path to the original source file that generated this
-//               chunk of code,
-//       originalLine: The line number in the original source that
-//                     corresponds to this chunk of generated code,
-//       originalColumn: The column number in the original source that
-//                       corresponds to this chunk of generated code,
-//       name: The name of the original symbol which generated this chunk of
-//             code.
-//     }
-//
-// All properties except for `generatedLine` and `generatedColumn` can be
-// `null`.
-//
-// `_generatedMappings` is ordered by the generated positions.
-//
-// `_originalMappings` is ordered by the original positions.
-
-SourceMapConsumer.prototype.__generatedMappings = null;
-Object.defineProperty(SourceMapConsumer.prototype, '_generatedMappings', {
-  configurable: true,
-  enumerable: true,
-  get: function () {
-    if (!this.__generatedMappings) {
-      this._parseMappings(this._mappings, this.sourceRoot);
+  /**
+   * Construct a new `SourceMapConsumer` from `rawSourceMap` and `sourceMapUrl`
+   * (see the `SourceMapConsumer` constructor for details. Then, invoke the `async
+   * function f(SourceMapConsumer) -> T` with the newly constructed consumer, wait
+   * for `f` to complete, call `destroy` on the consumer, and return `f`'s return
+   * value.
+   *
+   * You must not use the consumer after `f` completes!
+   *
+   * By using `with`, you do not have to remember to manually call `destroy` on
+   * the consumer, since it will be called automatically once `f` completes.
+   *
+   * ```js
+   * const xSquared = await SourceMapConsumer.with(
+   *   myRawSourceMap,
+   *   null,
+   *   async function (consumer) {
+   *     // Use `consumer` inside here and don't worry about remembering
+   *     // to call `destroy`.
+   *
+   *     const x = await whatever(consumer);
+   *     return x * x;
+   *   }
+   * );
+   *
+   * // You may not use that `consumer` anymore out here; it has
+   * // been destroyed. But you can use `xSquared`.
+   * console.log(xSquared);
+   * ```
+   */
+  static async with(rawSourceMap, sourceMapUrl, f) {
+    const consumer = await new SourceMapConsumer(rawSourceMap, sourceMapUrl);
+    try {
+      return await f(consumer);
+    } finally {
+      consumer.destroy();
     }
+  }
 
-    return this.__generatedMappings;
+  /**
+   * Parse the mappings in a string in to a data structure which we can easily
+   * query (the ordered arrays in the `this.__generatedMappings` and
+   * `this.__originalMappings` properties).
+   */
+  _parseMappings(aStr, aSourceRoot) {
+    throw new Error("Subclasses must implement _parseMappings");
   }
-});
 
-SourceMapConsumer.prototype.__originalMappings = null;
-Object.defineProperty(SourceMapConsumer.prototype, '_originalMappings', {
-  configurable: true,
-  enumerable: true,
-  get: function () {
-    if (!this.__originalMappings) {
-      this._parseMappings(this._mappings, this.sourceRoot);
-    }
+  /**
+   * Iterate over each mapping between an original source/line/column and a
+   * generated line/column in this source map.
+   *
+   * @param Function aCallback
+   *        The function that is called with each mapping.
+   * @param Object aContext
+   *        Optional. If specified, this object will be the value of `this` every
+   *        time that `aCallback` is called.
+   * @param aOrder
+   *        Either `SourceMapConsumer.GENERATED_ORDER` or
+   *        `SourceMapConsumer.ORIGINAL_ORDER`. Specifies whether you want to
+   *        iterate over the mappings sorted by the generated file's line/column
+   *        order or the original's source/line/column order, respectively. Defaults to
+   *        `SourceMapConsumer.GENERATED_ORDER`.
+   */
+  eachMapping(aCallback, aContext, aOrder) {
+    throw new Error("Subclasses must implement eachMapping");
+  }
 
-    return this.__originalMappings;
+  /**
+   * Returns all generated line and column information for the original source,
+   * line, and column provided. If no column is provided, returns all mappings
+   * corresponding to a either the line we are searching for or the next
+   * closest line that has any mappings. Otherwise, returns all mappings
+   * corresponding to the given line and either the column we are searching for
+   * or the next closest column that has any offsets.
+   *
+   * The only argument is an object with the following properties:
+   *
+   *   - source: The filename of the original source.
+   *   - line: The line number in the original source.  The line number is 1-based.
+   *   - column: Optional. the column number in the original source.
+   *    The column number is 0-based.
+   *
+   * and an array of objects is returned, each with the following properties:
+   *
+   *   - line: The line number in the generated source, or null.  The
+   *    line number is 1-based.
+   *   - column: The column number in the generated source, or null.
+   *    The column number is 0-based.
+   */
+  allGeneratedPositionsFor(aArgs) {
+    throw new Error("Subclasses must implement allGeneratedPositionsFor");
   }
-});
 
-SourceMapConsumer.prototype._charIsMappingSeparator =
-  function SourceMapConsumer_charIsMappingSeparator(aStr, index) {
-    var c = aStr.charAt(index);
-    return c === ";" || c === ",";
-  };
+  destroy() {
+    throw new Error("Subclasses must implement destroy");
+  }
+}
 
 /**
- * Parse the mappings in a string in to a data structure which we can easily
- * query (the ordered arrays in the `this.__generatedMappings` and
- * `this.__originalMappings` properties).
+ * The version of the source mapping spec that we are consuming.
  */
-SourceMapConsumer.prototype._parseMappings =
-  function SourceMapConsumer_parseMappings(aStr, aSourceRoot) {
-    throw new Error("Subclasses must implement _parseMappings");
-  };
-
+SourceMapConsumer.prototype._version = 3;
 SourceMapConsumer.GENERATED_ORDER = 1;
 SourceMapConsumer.ORIGINAL_ORDER = 2;
 
 SourceMapConsumer.GREATEST_LOWER_BOUND = 1;
 SourceMapConsumer.LEAST_UPPER_BOUND = 2;
 
-/**
- * Iterate over each mapping between an original source/line/column and a
- * generated line/column in this source map.
- *
- * @param Function aCallback
- *        The function that is called with each mapping.
- * @param Object aContext
- *        Optional. If specified, this object will be the value of `this` every
- *        time that `aCallback` is called.
- * @param aOrder
- *        Either `SourceMapConsumer.GENERATED_ORDER` or
- *        `SourceMapConsumer.ORIGINAL_ORDER`. Specifies whether you want to
- *        iterate over the mappings sorted by the generated file's line/column
- *        order or the original's source/line/column order, respectively. Defaults to
- *        `SourceMapConsumer.GENERATED_ORDER`.
- */
-SourceMapConsumer.prototype.eachMapping =
-  function SourceMapConsumer_eachMapping(aCallback, aContext, aOrder) {
-    var context = aContext || null;
-    var order = aOrder || SourceMapConsumer.GENERATED_ORDER;
-
-    var mappings;
-    switch (order) {
-    case SourceMapConsumer.GENERATED_ORDER:
-      mappings = this._generatedMappings;
-      break;
-    case SourceMapConsumer.ORIGINAL_ORDER:
-      mappings = this._originalMappings;
-      break;
-    default:
-      throw new Error("Unknown order of iteration.");
-    }
-
-    var sourceRoot = this.sourceRoot;
-    mappings.map(function (mapping) {
-      var source = mapping.source === null ? null : this._sources.at(mapping.source);
-      source = util.computeSourceURL(sourceRoot, source, this._sourceMapURL);
-      return {
-        source: source,
-        generatedLine: mapping.generatedLine,
-        generatedColumn: mapping.generatedColumn,
-        originalLine: mapping.originalLine,
-        originalColumn: mapping.originalColumn,
-        name: mapping.name === null ? null : this._names.at(mapping.name)
-      };
-    }, this).forEach(aCallback, context);
-  };
-
-/**
- * Returns all generated line and column information for the original source,
- * line, and column provided. If no column is provided, returns all mappings
- * corresponding to a either the line we are searching for or the next
- * closest line that has any mappings. Otherwise, returns all mappings
- * corresponding to the given line and either the column we are searching for
- * or the next closest column that has any offsets.
- *
- * The only argument is an object with the following properties:
- *
- *   - source: The filename of the original source.
- *   - line: The line number in the original source.  The line number is 1-based.
- *   - column: Optional. the column number in the original source.
- *    The column number is 0-based.
- *
- * and an array of objects is returned, each with the following properties:
- *
- *   - line: The line number in the generated source, or null.  The
- *    line number is 1-based.
- *   - column: The column number in the generated source, or null.
- *    The column number is 0-based.
- */
-SourceMapConsumer.prototype.allGeneratedPositionsFor =
-  function SourceMapConsumer_allGeneratedPositionsFor(aArgs) {
-    var line = util.getArg(aArgs, 'line');
-
-    // When there is no exact match, BasicSourceMapConsumer.prototype._findMapping
-    // returns the index of the closest mapping less than the needle. By
-    // setting needle.originalColumn to 0, we thus find the last mapping for
-    // the given line, provided such a mapping exists.
-    var needle = {
-      source: util.getArg(aArgs, 'source'),
-      originalLine: line,
-      originalColumn: util.getArg(aArgs, 'column', 0)
-    };
-
-    needle.source = this._findSourceIndex(needle.source);
-    if (needle.source < 0) {
-      return [];
-    }
-
-    var mappings = [];
-
-    var index = this._findMapping(needle,
-                                  this._originalMappings,
-                                  "originalLine",
-                                  "originalColumn",
-                                  util.compareByOriginalPositions,
-                                  binarySearch.LEAST_UPPER_BOUND);
-    if (index >= 0) {
-      var mapping = this._originalMappings[index];
-
-      if (aArgs.column === undefined) {
-        var originalLine = mapping.originalLine;
-
-        // Iterate until either we run out of mappings, or we run into
-        // a mapping for a different line than the one we found. Since
-        // mappings are sorted, this is guaranteed to find all mappings for
-        // the line we found.
-        while (mapping && mapping.originalLine === originalLine) {
-          mappings.push({
-            line: util.getArg(mapping, 'generatedLine', null),
-            column: util.getArg(mapping, 'generatedColumn', null),
-            lastColumn: util.getArg(mapping, 'lastGeneratedColumn', null)
-          });
-
-          mapping = this._originalMappings[++index];
-        }
-      } else {
-        var originalColumn = mapping.originalColumn;
-
-        // Iterate until either we run out of mappings, or we run into
-        // a mapping for a different line than the one we were searching for.
-        // Since mappings are sorted, this is guaranteed to find all mappings for
-        // the line we are searching for.
-        while (mapping &&
-               mapping.originalLine === line &&
-               mapping.originalColumn == originalColumn) {
-          mappings.push({
-            line: util.getArg(mapping, 'generatedLine', null),
-            column: util.getArg(mapping, 'generatedColumn', null),
-            lastColumn: util.getArg(mapping, 'lastGeneratedColumn', null)
-          });
-
-          mapping = this._originalMappings[++index];
-        }
-      }
-    }
-
-    return mappings;
-  };
-
 exports.SourceMapConsumer = SourceMapConsumer;
 
 /**
@@ -262,7 +156,7 @@ exports.SourceMapConsumer = SourceMapConsumer;
  *
  *   - version: Which version of the source map spec this map is following.
  *   - sources: An array of URLs to the original source files.
- *   - names: An array of identifiers which can be referrenced by individual mappings.
+ *   - names: An array of identifiers which can be referenced by individual mappings.
  *   - sourceRoot: Optional. The URL root from which all sources are relative.
  *   - sourcesContent: Optional. An array of contents of the original source files.
  *   - mappings: A string of base64 VLQs which contain the actual mappings.
@@ -285,398 +179,342 @@ exports.SourceMapConsumer = SourceMapConsumer;
  *
  * [0]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit?pli=1#
  */
-function BasicSourceMapConsumer(aSourceMap, aSourceMapURL) {
-  var sourceMap = aSourceMap;
-  if (typeof aSourceMap === 'string') {
-    sourceMap = util.parseSourceMapInput(aSourceMap);
-  }
+class BasicSourceMapConsumer extends SourceMapConsumer {
+  constructor(aSourceMap, aSourceMapURL) {
+    return super(INTERNAL).then(that => {
+      let sourceMap = aSourceMap;
+      if (typeof aSourceMap === "string") {
+        sourceMap = util.parseSourceMapInput(aSourceMap);
+      }
 
-  var version = util.getArg(sourceMap, 'version');
-  var sources = util.getArg(sourceMap, 'sources');
-  // Sass 3.3 leaves out the 'names' array, so we deviate from the spec (which
-  // requires the array) to play nice here.
-  var names = util.getArg(sourceMap, 'names', []);
-  var sourceRoot = util.getArg(sourceMap, 'sourceRoot', null);
-  var sourcesContent = util.getArg(sourceMap, 'sourcesContent', null);
-  var mappings = util.getArg(sourceMap, 'mappings');
-  var file = util.getArg(sourceMap, 'file', null);
-
-  // Once again, Sass deviates from the spec and supplies the version as a
-  // string rather than a number, so we use loose equality checking here.
-  if (version != this._version) {
-    throw new Error('Unsupported version: ' + version);
-  }
+      const version = util.getArg(sourceMap, "version");
+      let sources = util.getArg(sourceMap, "sources");
+      // Sass 3.3 leaves out the 'names' array, so we deviate from the spec (which
+      // requires the array) to play nice here.
+      const names = util.getArg(sourceMap, "names", []);
+      let sourceRoot = util.getArg(sourceMap, "sourceRoot", null);
+      const sourcesContent = util.getArg(sourceMap, "sourcesContent", null);
+      const mappings = util.getArg(sourceMap, "mappings");
+      const file = util.getArg(sourceMap, "file", null);
+
+      // Once again, Sass deviates from the spec and supplies the version as a
+      // string rather than a number, so we use loose equality checking here.
+      if (version != that._version) {
+        throw new Error("Unsupported version: " + version);
+      }
 
-  if (sourceRoot) {
-    sourceRoot = util.normalize(sourceRoot);
-  }
+      if (sourceRoot) {
+        sourceRoot = util.normalize(sourceRoot);
+      }
 
-  sources = sources
-    .map(String)
-    // Some source maps produce relative source paths like "./foo.js" instead of
-    // "foo.js".  Normalize these first so that future comparisons will succeed.
-    // See bugzil.la/1090768.
-    .map(util.normalize)
-    // Always ensure that absolute sources are internally stored relative to
-    // the source root, if the source root is absolute. Not doing this would
-    // be particularly problematic when the source root is a prefix of the
-    // source (valid, but why??). See github issue #199 and bugzil.la/1188982.
-    .map(function (source) {
-      return sourceRoot && util.isAbsolute(sourceRoot) && util.isAbsolute(source)
-        ? util.relative(sourceRoot, source)
-        : source;
-    });
+      sources = sources
+        .map(String)
+        // Some source maps produce relative source paths like "./foo.js" instead of
+        // "foo.js".  Normalize these first so that future comparisons will succeed.
+        // See bugzil.la/1090768.
+        .map(util.normalize)
+        // Always ensure that absolute sources are internally stored relative to
+        // the source root, if the source root is absolute. Not doing this would
+        // be particularly problematic when the source root is a prefix of the
+        // source (valid, but why??). See github issue #199 and bugzil.la/1188982.
+        .map(function(source) {
+          return sourceRoot && util.isAbsolute(sourceRoot) && util.isAbsolute(source)
+            ? util.relative(sourceRoot, source)
+            : source;
+        });
+
+      // Pass `true` below to allow duplicate names and sources. While source maps
+      // are intended to be compressed and deduplicated, the TypeScript compiler
+      // sometimes generates source maps with duplicates in them. See Github issue
+      // #72 and bugzil.la/889492.
+      that._names = ArraySet.fromArray(names.map(String), true);
+      that._sources = ArraySet.fromArray(sources, true);
+
+      that._absoluteSources = that._sources.toArray().map(function(s) {
+        return util.computeSourceURL(sourceRoot, s, aSourceMapURL);
+      });
 
-  // Pass `true` below to allow duplicate names and sources. While source maps
-  // are intended to be compressed and deduplicated, the TypeScript compiler
-  // sometimes generates source maps with duplicates in them. See Github issue
-  // #72 and bugzil.la/889492.
-  this._names = ArraySet.fromArray(names.map(String), true);
-  this._sources = ArraySet.fromArray(sources, true);
-
-  this._absoluteSources = this._sources.toArray().map(function (s) {
-    return util.computeSourceURL(sourceRoot, s, aSourceMapURL);
-  });
-
-  this.sourceRoot = sourceRoot;
-  this.sourcesContent = sourcesContent;
-  this._mappings = mappings;
-  this._sourceMapURL = aSourceMapURL;
-  this.file = file;
-}
+      that.sourceRoot = sourceRoot;
+      that.sourcesContent = sourcesContent;
+      that._mappings = mappings;
+      that._sourceMapURL = aSourceMapURL;
+      that.file = file;
 
-BasicSourceMapConsumer.prototype = Object.create(SourceMapConsumer.prototype);
-BasicSourceMapConsumer.prototype.consumer = SourceMapConsumer;
+      that._computedColumnSpans = false;
+      that._mappingsPtr = 0;
+      that._wasm = null;
 
-/**
- * Utility function to find the index of a source.  Returns -1 if not
- * found.
- */
-BasicSourceMapConsumer.prototype._findSourceIndex = function(aSource) {
-  var relativeSource = aSource;
-  if (this.sourceRoot != null) {
-    relativeSource = util.relative(this.sourceRoot, relativeSource);
+      return wasm().then(w => {
+        that._wasm = w;
+        return that;
+      });
+    });
   }
 
-  if (this._sources.has(relativeSource)) {
-    return this._sources.indexOf(relativeSource);
-  }
+  /**
+   * Utility function to find the index of a source.  Returns -1 if not
+   * found.
+   */
+  _findSourceIndex(aSource) {
+    let relativeSource = aSource;
+    if (this.sourceRoot != null) {
+      relativeSource = util.relative(this.sourceRoot, relativeSource);
+    }
 
-  // Maybe aSource is an absolute URL as returned by |sources|.  In
-  // this case we can't simply undo the transform.
-  var i;
-  for (i = 0; i < this._absoluteSources.length; ++i) {
-    if (this._absoluteSources[i] == aSource) {
-      return i;
+    if (this._sources.has(relativeSource)) {
+      return this._sources.indexOf(relativeSource);
     }
-  }
 
-  return -1;
-};
+    // Maybe aSource is an absolute URL as returned by |sources|.  In
+    // this case we can't simply undo the transform.
+    for (let i = 0; i < this._absoluteSources.length; ++i) {
+      if (this._absoluteSources[i] == aSource) {
+        return i;
+      }
+    }
 
-/**
- * Create a BasicSourceMapConsumer from a SourceMapGenerator.
- *
- * @param SourceMapGenerator aSourceMap
- *        The source map that will be consumed.
- * @param String aSourceMapURL
- *        The URL at which the source map can be found (optional)
- * @returns BasicSourceMapConsumer
- */
-BasicSourceMapConsumer.fromSourceMap =
-  function SourceMapConsumer_fromSourceMap(aSourceMap, aSourceMapURL) {
-    var smc = Object.create(BasicSourceMapConsumer.prototype);
-
-    var names = smc._names = ArraySet.fromArray(aSourceMap._names.toArray(), true);
-    var sources = smc._sources = ArraySet.fromArray(aSourceMap._sources.toArray(), true);
-    smc.sourceRoot = aSourceMap._sourceRoot;
-    smc.sourcesContent = aSourceMap._generateSourcesContent(smc._sources.toArray(),
-                                                            smc.sourceRoot);
-    smc.file = aSourceMap._file;
-    smc._sourceMapURL = aSourceMapURL;
-    smc._absoluteSources = smc._sources.toArray().map(function (s) {
-      return util.computeSourceURL(smc.sourceRoot, s, aSourceMapURL);
-    });
+    return -1;
+  }
 
-    // Because we are modifying the entries (by converting string sources and
-    // names to indices into the sources and names ArraySets), we have to make
-    // a copy of the entry or else bad things happen. Shared mutable state
-    // strikes again! See github issue #191.
+  /**
+   * Create a BasicSourceMapConsumer from a SourceMapGenerator.
+   *
+   * @param SourceMapGenerator aSourceMap
+   *        The source map that will be consumed.
+   * @param String aSourceMapURL
+   *        The URL at which the source map can be found (optional)
+   * @returns BasicSourceMapConsumer
+   */
+  static fromSourceMap(aSourceMap, aSourceMapURL) {
+    return new BasicSourceMapConsumer(aSourceMap.toString());
+  }
 
-    var generatedMappings = aSourceMap._mappings.toArray().slice();
-    var destGeneratedMappings = smc.__generatedMappings = [];
-    var destOriginalMappings = smc.__originalMappings = [];
+  get sources() {
+    return this._absoluteSources.slice();
+  }
 
-    for (var i = 0, length = generatedMappings.length; i < length; i++) {
-      var srcMapping = generatedMappings[i];
-      var destMapping = new Mapping;
-      destMapping.generatedLine = srcMapping.generatedLine;
-      destMapping.generatedColumn = srcMapping.generatedColumn;
+  _getMappingsPtr() {
+    if (this._mappingsPtr === 0) {
+      this._parseMappings(this._mappings, this.sourceRoot);
+    }
 
-      if (srcMapping.source) {
-        destMapping.source = sources.indexOf(srcMapping.source);
-        destMapping.originalLine = srcMapping.originalLine;
-        destMapping.originalColumn = srcMapping.originalColumn;
+    return this._mappingsPtr;
+  }
 
-        if (srcMapping.name) {
-          destMapping.name = names.indexOf(srcMapping.name);
-        }
+  /**
+   * Parse the mappings in a string in to a data structure which we can easily
+   * query (the ordered arrays in the `this.__generatedMappings` and
+   * `this.__originalMappings` properties).
+   */
+  _parseMappings(aStr, aSourceRoot) {
+    const size = aStr.length;
+
+    const mappingsBufPtr = this._wasm.exports.allocate_mappings(size);
+    const mappingsBuf = new Uint8Array(this._wasm.exports.memory.buffer, mappingsBufPtr, size);
+    for (let i = 0; i < size; i++) {
+      mappingsBuf[i] = aStr.charCodeAt(i);
+    }
 
-        destOriginalMappings.push(destMapping);
+    const mappingsPtr = this._wasm.exports.parse_mappings(mappingsBufPtr);
+
+    if (!mappingsPtr) {
+      const error = this._wasm.exports.get_last_error();
+      let msg = `Error parsing mappings (code ${error}): `;
+
+      // XXX: keep these error codes in sync with `fitzgen/source-map-mappings`.
+      switch (error) {
+        case 1:
+          msg += "the mappings contained a negative line, column, source index, or name index";
+          break;
+        case 2:
+          msg += "the mappings contained a number larger than 2**32";
+          break;
+        case 3:
+          msg += "reached EOF while in the middle of parsing a VLQ";
+          break;
+        case 4:
+          msg += "invalid base 64 character while parsing a VLQ";
+          break;
+        default:
+          msg += "unknown error code";
+          break;
       }
 
-      destGeneratedMappings.push(destMapping);
+      throw new Error(msg);
     }
 
-    quickSort(smc.__originalMappings, util.compareByOriginalPositions);
-
-    return smc;
-  };
-
-/**
- * The version of the source mapping spec that we are consuming.
- */
-BasicSourceMapConsumer.prototype._version = 3;
-
-/**
- * The list of original sources.
- */
-Object.defineProperty(BasicSourceMapConsumer.prototype, 'sources', {
-  get: function () {
-    return this._absoluteSources.slice();
+    this._mappingsPtr = mappingsPtr;
   }
-});
 
-/**
- * Provide the JIT with a nice shape / hidden class.
- */
-function Mapping() {
-  this.generatedLine = 0;
-  this.generatedColumn = 0;
-  this.source = null;
-  this.originalLine = null;
-  this.originalColumn = null;
-  this.name = null;
-}
-
-/**
- * Parse the mappings in a string in to a data structure which we can easily
- * query (the ordered arrays in the `this.__generatedMappings` and
- * `this.__originalMappings` properties).
- */
-BasicSourceMapConsumer.prototype._parseMappings =
-  function SourceMapConsumer_parseMappings(aStr, aSourceRoot) {
-    var generatedLine = 1;
-    var previousGeneratedColumn = 0;
-    var previousOriginalLine = 0;
-    var previousOriginalColumn = 0;
-    var previousSource = 0;
-    var previousName = 0;
-    var length = aStr.length;
-    var index = 0;
-    var cachedSegments = {};
-    var temp = {};
-    var originalMappings = [];
-    var generatedMappings = [];
-    var mapping, str, segment, end, value;
-
-    while (index < length) {
-      if (aStr.charAt(index) === ';') {
-        generatedLine++;
-        index++;
-        previousGeneratedColumn = 0;
-      }
-      else if (aStr.charAt(index) === ',') {
-        index++;
-      }
-      else {
-        mapping = new Mapping();
-        mapping.generatedLine = generatedLine;
-
-        // Because each offset is encoded relative to the previous one,
-        // many segments often have the same encoding. We can exploit this
-        // fact by caching the parsed variable length fields of each segment,
-        // allowing us to avoid a second parse if we encounter the same
-        // segment again.
-        for (end = index; end < length; end++) {
-          if (this._charIsMappingSeparator(aStr, end)) {
-            break;
-          }
-        }
-        str = aStr.slice(index, end);
-
-        segment = cachedSegments[str];
-        if (segment) {
-          index += str.length;
-        } else {
-          segment = [];
-          while (index < end) {
-            base64VLQ.decode(aStr, index, temp);
-            value = temp.value;
-            index = temp.rest;
-            segment.push(value);
-          }
-
-          if (segment.length === 2) {
-            throw new Error('Found a source, but no line and column');
-          }
+  eachMapping(aCallback, aContext, aOrder) {
+    const context = aContext || null;
+    const order = aOrder || SourceMapConsumer.GENERATED_ORDER;
+    const sourceRoot = this.sourceRoot;
 
-          if (segment.length === 3) {
-            throw new Error('Found a source and line, but no column');
-          }
-
-          cachedSegments[str] = segment;
-        }
+    this._wasm.withMappingCallback(
+      mapping => {
+        if (mapping.source !== null) {
+          mapping.source = this._sources.at(mapping.source);
+          mapping.source = util.computeSourceURL(sourceRoot, mapping.source, this._sourceMapURL);
 
-        // Generated column.
-        mapping.generatedColumn = previousGeneratedColumn + segment[0];
-        previousGeneratedColumn = mapping.generatedColumn;
-
-        if (segment.length > 1) {
-          // Original source.
-          mapping.source = previousSource + segment[1];
-          previousSource += segment[1];
-
-          // Original line.
-          mapping.originalLine = previousOriginalLine + segment[2];
-          previousOriginalLine = mapping.originalLine;
-          // Lines are stored 0-based
-          mapping.originalLine += 1;
-
-          // Original column.
-          mapping.originalColumn = previousOriginalColumn + segment[3];
-          previousOriginalColumn = mapping.originalColumn;
-
-          if (segment.length > 4) {
-            // Original name.
-            mapping.name = previousName + segment[4];
-            previousName += segment[4];
+          if (mapping.name !== null) {
+            mapping.name = this._names.at(mapping.name);
           }
         }
 
-        generatedMappings.push(mapping);
-        if (typeof mapping.originalLine === 'number') {
-          originalMappings.push(mapping);
+        aCallback.call(context, mapping);
+      },
+      () => {
+        switch (order) {
+        case SourceMapConsumer.GENERATED_ORDER:
+          this._wasm.exports.by_generated_location(this._getMappingsPtr());
+          break;
+        case SourceMapConsumer.ORIGINAL_ORDER:
+          this._wasm.exports.by_original_location(this._getMappingsPtr());
+          break;
+        default:
+          throw new Error("Unknown order of iteration.");
         }
       }
-    }
-
-    quickSort(generatedMappings, util.compareByGeneratedPositionsDeflated);
-    this.__generatedMappings = generatedMappings;
+    );
+  }
 
-    quickSort(originalMappings, util.compareByOriginalPositions);
-    this.__originalMappings = originalMappings;
-  };
+  allGeneratedPositionsFor(aArgs) {
+    let source = util.getArg(aArgs, "source");
+    const originalLine = util.getArg(aArgs, "line");
+    const originalColumn = aArgs.column || 0;
 
-/**
- * Find the mapping that best matches the hypothetical "needle" mapping that
- * we are searching for in the given "haystack" of mappings.
- */
-BasicSourceMapConsumer.prototype._findMapping =
-  function SourceMapConsumer_findMapping(aNeedle, aMappings, aLineName,
-                                         aColumnName, aComparator, aBias) {
-    // To return the position we are searching for, we must first find the
-    // mapping for the given position and then return the opposite position it
-    // points to. Because the mappings are sorted, we can use binary search to
-    // find the best mapping.
+    source = this._findSourceIndex(source);
+    if (source < 0) {
+      return [];
+    }
 
-    if (aNeedle[aLineName] <= 0) {
-      throw new TypeError('Line must be greater than or equal to 1, got '
-                          + aNeedle[aLineName]);
+    if (originalLine < 1) {
+      throw new Error("Line numbers must be >= 1");
     }
-    if (aNeedle[aColumnName] < 0) {
-      throw new TypeError('Column must be greater than or equal to 0, got '
-                          + aNeedle[aColumnName]);
+
+    if (originalColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
     }
 
-    return binarySearch.search(aNeedle, aMappings, aComparator, aBias);
-  };
+    const mappings = [];
 
-/**
- * Compute the last column for each generated mapping. The last column is
- * inclusive.
- */
-BasicSourceMapConsumer.prototype.computeColumnSpans =
-  function SourceMapConsumer_computeColumnSpans() {
-    for (var index = 0; index < this._generatedMappings.length; ++index) {
-      var mapping = this._generatedMappings[index];
-
-      // Mappings do not contain a field for the last generated columnt. We
-      // can come up with an optimistic estimate, however, by assuming that
-      // mappings are contiguous (i.e. given two consecutive mappings, the
-      // first mapping ends where the second one starts).
-      if (index + 1 < this._generatedMappings.length) {
-        var nextMapping = this._generatedMappings[index + 1];
-
-        if (mapping.generatedLine === nextMapping.generatedLine) {
-          mapping.lastGeneratedColumn = nextMapping.generatedColumn - 1;
-          continue;
+    this._wasm.withMappingCallback(
+      m => {
+        let lastColumn = m.lastGeneratedColumn;
+        if (this._computedColumnSpans && lastColumn === null) {
+          lastColumn = Infinity;
         }
+        mappings.push({
+          line: m.generatedLine,
+          column: m.generatedColumn,
+          lastColumn,
+        });
+      }, () => {
+        this._wasm.exports.all_generated_locations_for(
+          this._getMappingsPtr(),
+          source,
+          originalLine - 1,
+          "column" in aArgs,
+          originalColumn
+        );
       }
+    );
+
+    return mappings;
+  }
 
-      // The last mapping for each line spans the entire line.
-      mapping.lastGeneratedColumn = Infinity;
+  destroy() {
+    if (this._mappingsPtr !== 0) {
+      this._wasm.exports.free_mappings(this._mappingsPtr);
+      this._mappingsPtr = 0;
     }
-  };
+  }
 
-/**
- * Returns the original source, line, and column information for the generated
- * source's line and column positions provided. The only argument is an object
- * with the following properties:
- *
- *   - line: The line number in the generated source.  The line number
- *     is 1-based.
- *   - column: The column number in the generated source.  The column
- *     number is 0-based.
- *   - bias: Either 'SourceMapConsumer.GREATEST_LOWER_BOUND' or
- *     'SourceMapConsumer.LEAST_UPPER_BOUND'. Specifies whether to return the
- *     closest element that is smaller than or greater than the one we are
- *     searching for, respectively, if the exact element cannot be found.
- *     Defaults to 'SourceMapConsumer.GREATEST_LOWER_BOUND'.
- *
- * and an object is returned with the following properties:
- *
- *   - source: The original source file, or null.
- *   - line: The line number in the original source, or null.  The
- *     line number is 1-based.
- *   - column: The column number in the original source, or null.  The
- *     column number is 0-based.
- *   - name: The original identifier, or null.
- */
-BasicSourceMapConsumer.prototype.originalPositionFor =
-  function SourceMapConsumer_originalPositionFor(aArgs) {
-    var needle = {
-      generatedLine: util.getArg(aArgs, 'line'),
-      generatedColumn: util.getArg(aArgs, 'column')
+  /**
+   * Compute the last column for each generated mapping. The last column is
+   * inclusive.
+   */
+  computeColumnSpans() {
+    if (this._computedColumnSpans) {
+      return;
+    }
+
+    this._wasm.exports.compute_column_spans(this._getMappingsPtr());
+    this._computedColumnSpans = true;
+  }
+
+  /**
+   * Returns the original source, line, and column information for the generated
+   * source's line and column positions provided. The only argument is an object
+   * with the following properties:
+   *
+   *   - line: The line number in the generated source.  The line number
+   *     is 1-based.
+   *   - column: The column number in the generated source.  The column
+   *     number is 0-based.
+   *   - bias: Either 'SourceMapConsumer.GREATEST_LOWER_BOUND' or
+   *     'SourceMapConsumer.LEAST_UPPER_BOUND'. Specifies whether to return the
+   *     closest element that is smaller than or greater than the one we are
+   *     searching for, respectively, if the exact element cannot be found.
+   *     Defaults to 'SourceMapConsumer.GREATEST_LOWER_BOUND'.
+   *
+   * and an object is returned with the following properties:
+   *
+   *   - source: The original source file, or null.
+   *   - line: The line number in the original source, or null.  The
+   *     line number is 1-based.
+   *   - column: The column number in the original source, or null.  The
+   *     column number is 0-based.
+   *   - name: The original identifier, or null.
+   */
+  originalPositionFor(aArgs) {
+    const needle = {
+      generatedLine: util.getArg(aArgs, "line"),
+      generatedColumn: util.getArg(aArgs, "column")
     };
 
-    var index = this._findMapping(
-      needle,
-      this._generatedMappings,
-      "generatedLine",
-      "generatedColumn",
-      util.compareByGeneratedPositionsDeflated,
-      util.getArg(aArgs, 'bias', SourceMapConsumer.GREATEST_LOWER_BOUND)
-    );
+    if (needle.generatedLine < 1) {
+      throw new Error("Line numbers must be >= 1");
+    }
 
-    if (index >= 0) {
-      var mapping = this._generatedMappings[index];
+    if (needle.generatedColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
+    }
 
+    let bias = util.getArg(aArgs, "bias", SourceMapConsumer.GREATEST_LOWER_BOUND);
+    if (bias == null) {
+      bias = SourceMapConsumer.GREATEST_LOWER_BOUND;
+    }
+
+    let mapping;
+    this._wasm.withMappingCallback(m => mapping = m, () => {
+      this._wasm.exports.original_location_for(
+        this._getMappingsPtr(),
+        needle.generatedLine - 1,
+        needle.generatedColumn,
+        bias
+      );
+    });
+
+    if (mapping) {
       if (mapping.generatedLine === needle.generatedLine) {
-        var source = util.getArg(mapping, 'source', null);
+        let source = util.getArg(mapping, "source", null);
         if (source !== null) {
           source = this._sources.at(source);
           source = util.computeSourceURL(this.sourceRoot, source, this._sourceMapURL);
         }
-        var name = util.getArg(mapping, 'name', null);
+
+        let name = util.getArg(mapping, "name", null);
         if (name !== null) {
           name = this._names.at(name);
         }
+
         return {
-          source: source,
-          line: util.getArg(mapping, 'originalLine', null),
-          column: util.getArg(mapping, 'originalColumn', null),
-          name: name
+          source,
+          line: util.getArg(mapping, "originalLine", null),
+          column: util.getArg(mapping, "originalColumn", null),
+          name
         };
       }
     }
@@ -687,53 +525,51 @@ BasicSourceMapConsumer.prototype.originalPositionFor =
       column: null,
       name: null
     };
-  };
+  }
 
-/**
- * Return true if we have the source content for every source in the source
- * map, false otherwise.
- */
-BasicSourceMapConsumer.prototype.hasContentsOfAllSources =
-  function BasicSourceMapConsumer_hasContentsOfAllSources() {
+  /**
+   * Return true if we have the source content for every source in the source
+   * map, false otherwise.
+   */
+  hasContentsOfAllSources() {
     if (!this.sourcesContent) {
       return false;
     }
     return this.sourcesContent.length >= this._sources.size() &&
-      !this.sourcesContent.some(function (sc) { return sc == null; });
-  };
+      !this.sourcesContent.some(function(sc) { return sc == null; });
+  }
 
-/**
- * Returns the original source content. The only argument is the url of the
- * original source file. Returns null if no original source content is
- * available.
- */
-BasicSourceMapConsumer.prototype.sourceContentFor =
-  function SourceMapConsumer_sourceContentFor(aSource, nullOnMissing) {
+  /**
+   * Returns the original source content. The only argument is the url of the
+   * original source file. Returns null if no original source content is
+   * available.
+   */
+  sourceContentFor(aSource, nullOnMissing) {
     if (!this.sourcesContent) {
       return null;
     }
 
-    var index = this._findSourceIndex(aSource);
+    const index = this._findSourceIndex(aSource);
     if (index >= 0) {
       return this.sourcesContent[index];
     }
 
-    var relativeSource = aSource;
+    let relativeSource = aSource;
     if (this.sourceRoot != null) {
       relativeSource = util.relative(this.sourceRoot, relativeSource);
     }
 
-    var url;
+    let url;
     if (this.sourceRoot != null
         && (url = util.urlParse(this.sourceRoot))) {
       // XXX: file:// URIs and absolute paths lead to unexpected behavior for
       // many users. We can help them out when they expect file:// URIs to
       // behave like it would if they were running a local HTTP server. See
       // https://bugzilla.mozilla.org/show_bug.cgi?id=885597.
-      var fileUriAbsPath = relativeSource.replace(/^file:\/\//, "");
+      const fileUriAbsPath = relativeSource.replace(/^file:\/\//, "");
       if (url.scheme == "file"
           && this._sources.has(fileUriAbsPath)) {
-        return this.sourcesContent[this._sources.indexOf(fileUriAbsPath)]
+        return this.sourcesContent[this._sources.indexOf(fileUriAbsPath)];
       }
 
       if ((!url.path || url.path == "/")
@@ -749,37 +585,35 @@ BasicSourceMapConsumer.prototype.sourceContentFor =
     if (nullOnMissing) {
       return null;
     }
-    else {
-      throw new Error('"' + relativeSource + '" is not in the SourceMap.');
-    }
-  };
 
-/**
- * Returns the generated line and column information for the original source,
- * line, and column positions provided. The only argument is an object with
- * the following properties:
- *
- *   - source: The filename of the original source.
- *   - line: The line number in the original source.  The line number
- *     is 1-based.
- *   - column: The column number in the original source.  The column
- *     number is 0-based.
- *   - bias: Either 'SourceMapConsumer.GREATEST_LOWER_BOUND' or
- *     'SourceMapConsumer.LEAST_UPPER_BOUND'. Specifies whether to return the
- *     closest element that is smaller than or greater than the one we are
- *     searching for, respectively, if the exact element cannot be found.
- *     Defaults to 'SourceMapConsumer.GREATEST_LOWER_BOUND'.
- *
- * and an object is returned with the following properties:
- *
- *   - line: The line number in the generated source, or null.  The
- *     line number is 1-based.
- *   - column: The column number in the generated source, or null.
- *     The column number is 0-based.
- */
-BasicSourceMapConsumer.prototype.generatedPositionFor =
-  function SourceMapConsumer_generatedPositionFor(aArgs) {
-    var source = util.getArg(aArgs, 'source');
+    throw new Error('"' + relativeSource + '" is not in the SourceMap.');
+  }
+
+  /**
+   * Returns the generated line and column information for the original source,
+   * line, and column positions provided. The only argument is an object with
+   * the following properties:
+   *
+   *   - source: The filename of the original source.
+   *   - line: The line number in the original source.  The line number
+   *     is 1-based.
+   *   - column: The column number in the original source.  The column
+   *     number is 0-based.
+   *   - bias: Either 'SourceMapConsumer.GREATEST_LOWER_BOUND' or
+   *     'SourceMapConsumer.LEAST_UPPER_BOUND'. Specifies whether to return the
+   *     closest element that is smaller than or greater than the one we are
+   *     searching for, respectively, if the exact element cannot be found.
+   *     Defaults to 'SourceMapConsumer.GREATEST_LOWER_BOUND'.
+   *
+   * and an object is returned with the following properties:
+   *
+   *   - line: The line number in the generated source, or null.  The
+   *     line number is 1-based.
+   *   - column: The column number in the generated source, or null.
+   *     The column number is 0-based.
+   */
+  generatedPositionFor(aArgs) {
+    let source = util.getArg(aArgs, "source");
     source = this._findSourceIndex(source);
     if (source < 0) {
       return {
@@ -789,29 +623,46 @@ BasicSourceMapConsumer.prototype.generatedPositionFor =
       };
     }
 
-    var needle = {
-      source: source,
-      originalLine: util.getArg(aArgs, 'line'),
-      originalColumn: util.getArg(aArgs, 'column')
+    const needle = {
+      source,
+      originalLine: util.getArg(aArgs, "line"),
+      originalColumn: util.getArg(aArgs, "column")
     };
 
-    var index = this._findMapping(
-      needle,
-      this._originalMappings,
-      "originalLine",
-      "originalColumn",
-      util.compareByOriginalPositions,
-      util.getArg(aArgs, 'bias', SourceMapConsumer.GREATEST_LOWER_BOUND)
-    );
+    if (needle.originalLine < 1) {
+      throw new Error("Line numbers must be >= 1");
+    }
 
-    if (index >= 0) {
-      var mapping = this._originalMappings[index];
+    if (needle.originalColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
+    }
 
+    let bias = util.getArg(aArgs, "bias", SourceMapConsumer.GREATEST_LOWER_BOUND);
+    if (bias == null) {
+      bias = SourceMapConsumer.GREATEST_LOWER_BOUND;
+    }
+
+    let mapping;
+    this._wasm.withMappingCallback(m => mapping = m, () => {
+      this._wasm.exports.generated_location_for(
+        this._getMappingsPtr(),
+        needle.source,
+        needle.originalLine - 1,
+        needle.originalColumn,
+        bias
+      );
+    });
+
+    if (mapping) {
       if (mapping.source === needle.source) {
+        let lastColumn = mapping.lastGeneratedColumn;
+        if (this._computedColumnSpans && lastColumn === null) {
+          lastColumn = Infinity;
+        }
         return {
-          line: util.getArg(mapping, 'generatedLine', null),
-          column: util.getArg(mapping, 'generatedColumn', null),
-          lastColumn: util.getArg(mapping, 'lastGeneratedColumn', null)
+          line: util.getArg(mapping, "generatedLine", null),
+          column: util.getArg(mapping, "generatedColumn", null),
+          lastColumn,
         };
       }
     }
@@ -821,8 +672,10 @@ BasicSourceMapConsumer.prototype.generatedPositionFor =
       column: null,
       lastColumn: null
     };
-  };
+  }
+}
 
+BasicSourceMapConsumer.prototype.consumer = SourceMapConsumer;
 exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
 
 /**
@@ -874,116 +727,191 @@ exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
  *
  * [0]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit#heading=h.535es3xeprgt
  */
-function IndexedSourceMapConsumer(aSourceMap, aSourceMapURL) {
-  var sourceMap = aSourceMap;
-  if (typeof aSourceMap === 'string') {
-    sourceMap = util.parseSourceMapInput(aSourceMap);
+class IndexedSourceMapConsumer extends SourceMapConsumer {
+  constructor(aSourceMap, aSourceMapURL) {
+    return super(INTERNAL).then(that => {
+      let sourceMap = aSourceMap;
+      if (typeof aSourceMap === "string") {
+        sourceMap = util.parseSourceMapInput(aSourceMap);
+      }
+
+      const version = util.getArg(sourceMap, "version");
+      const sections = util.getArg(sourceMap, "sections");
+
+      if (version != that._version) {
+        throw new Error("Unsupported version: " + version);
+      }
+
+      that._sources = new ArraySet();
+      that._names = new ArraySet();
+      that.__generatedMappings = null;
+      that.__originalMappings = null;
+      that.__generatedMappingsUnsorted = null;
+      that.__originalMappingsUnsorted = null;
+
+      let lastOffset = {
+        line: -1,
+        column: 0
+      };
+      return Promise.all(sections.map(s => {
+        if (s.url) {
+          // The url field will require support for asynchronicity.
+          // See https://github.com/mozilla/source-map/issues/16
+          throw new Error("Support for url field in sections not implemented.");
+        }
+        const offset = util.getArg(s, "offset");
+        const offsetLine = util.getArg(offset, "line");
+        const offsetColumn = util.getArg(offset, "column");
+
+        if (offsetLine < lastOffset.line ||
+            (offsetLine === lastOffset.line && offsetColumn < lastOffset.column)) {
+          throw new Error("Section offsets must be ordered and non-overlapping.");
+        }
+        lastOffset = offset;
+
+        const cons = new SourceMapConsumer(util.getArg(s, "map"), aSourceMapURL);
+        return cons.then(consumer => {
+          return {
+            generatedOffset: {
+              // The offset fields are 0-based, but we use 1-based indices when
+              // encoding/decoding from VLQ.
+              generatedLine: offsetLine + 1,
+              generatedColumn: offsetColumn + 1
+            },
+            consumer
+          };
+        });
+      })).then(s => {
+        that._sections = s;
+        return that;
+      });
+    });
   }
 
-  var version = util.getArg(sourceMap, 'version');
-  var sections = util.getArg(sourceMap, 'sections');
+  // `__generatedMappings` and `__originalMappings` are arrays that hold the
+  // parsed mapping coordinates from the source map's "mappings" attribute. They
+  // are lazily instantiated, accessed via the `_generatedMappings` and
+  // `_originalMappings` getters respectively, and we only parse the mappings
+  // and create these arrays once queried for a source location. We jump through
+  // these hoops because there can be many thousands of mappings, and parsing
+  // them is expensive, so we only want to do it if we must.
+  //
+  // Each object in the arrays is of the form:
+  //
+  //     {
+  //       generatedLine: The line number in the generated code,
+  //       generatedColumn: The column number in the generated code,
+  //       source: The path to the original source file that generated this
+  //               chunk of code,
+  //       originalLine: The line number in the original source that
+  //                     corresponds to this chunk of generated code,
+  //       originalColumn: The column number in the original source that
+  //                       corresponds to this chunk of generated code,
+  //       name: The name of the original symbol which generated this chunk of
+  //             code.
+  //     }
+  //
+  // All properties except for `generatedLine` and `generatedColumn` can be
+  // `null`.
+  //
+  // `_generatedMappings` is ordered by the generated positions.
+  //
+  // `_originalMappings` is ordered by the original positions.
+  get _generatedMappings() {
+    if (!this.__generatedMappings) {
+      this._sortGeneratedMappings();
+    }
 
-  if (version != this._version) {
-    throw new Error('Unsupported version: ' + version);
+    return this.__generatedMappings;
   }
 
-  this._sources = new ArraySet();
-  this._names = new ArraySet();
-
-  var lastOffset = {
-    line: -1,
-    column: 0
-  };
-  this._sections = sections.map(function (s) {
-    if (s.url) {
-      // The url field will require support for asynchronicity.
-      // See https://github.com/mozilla/source-map/issues/16
-      throw new Error('Support for url field in sections not implemented.');
+  get _originalMappings() {
+    if (!this.__originalMappings) {
+      this._sortOriginalMappings();
     }
-    var offset = util.getArg(s, 'offset');
-    var offsetLine = util.getArg(offset, 'line');
-    var offsetColumn = util.getArg(offset, 'column');
 
-    if (offsetLine < lastOffset.line ||
-        (offsetLine === lastOffset.line && offsetColumn < lastOffset.column)) {
-      throw new Error('Section offsets must be ordered and non-overlapping.');
+    return this.__originalMappings;
+  }
+
+  get _generatedMappingsUnsorted() {
+    if (!this.__generatedMappingsUnsorted) {
+      this._parseMappings(this._mappings, this.sourceRoot);
     }
-    lastOffset = offset;
 
-    return {
-      generatedOffset: {
-        // The offset fields are 0-based, but we use 1-based indices when
-        // encoding/decoding from VLQ.
-        generatedLine: offsetLine + 1,
-        generatedColumn: offsetColumn + 1
-      },
-      consumer: new SourceMapConsumer(util.getArg(s, 'map'), aSourceMapURL)
+    return this.__generatedMappingsUnsorted;
+  }
+
+  get _originalMappingsUnsorted() {
+    if (!this.__originalMappingsUnsorted) {
+      this._parseMappings(this._mappings, this.sourceRoot);
     }
-  });
-}
 
-IndexedSourceMapConsumer.prototype = Object.create(SourceMapConsumer.prototype);
-IndexedSourceMapConsumer.prototype.constructor = SourceMapConsumer;
+    return this.__originalMappingsUnsorted;
+  }
 
-/**
- * The version of the source mapping spec that we are consuming.
- */
-IndexedSourceMapConsumer.prototype._version = 3;
+  _sortGeneratedMappings() {
+    const mappings = this._generatedMappingsUnsorted;
+    mappings.sort(util.compareByGeneratedPositionsDeflated);
+    this.__generatedMappings = mappings;
+  }
 
-/**
- * The list of original sources.
- */
-Object.defineProperty(IndexedSourceMapConsumer.prototype, 'sources', {
-  get: function () {
-    var sources = [];
-    for (var i = 0; i < this._sections.length; i++) {
-      for (var j = 0; j < this._sections[i].consumer.sources.length; j++) {
+  _sortOriginalMappings() {
+    const mappings = this._originalMappingsUnsorted;
+    mappings.sort(util.compareByOriginalPositions);
+    this.__originalMappings = mappings;
+  }
+
+  /**
+   * The list of original sources.
+   */
+  get sources() {
+    const sources = [];
+    for (let i = 0; i < this._sections.length; i++) {
+      for (let j = 0; j < this._sections[i].consumer.sources.length; j++) {
         sources.push(this._sections[i].consumer.sources[j]);
       }
     }
     return sources;
   }
-});
 
-/**
- * Returns the original source, line, and column information for the generated
- * source's line and column positions provided. The only argument is an object
- * with the following properties:
- *
- *   - line: The line number in the generated source.  The line number
- *     is 1-based.
- *   - column: The column number in the generated source.  The column
- *     number is 0-based.
- *
- * and an object is returned with the following properties:
- *
- *   - source: The original source file, or null.
- *   - line: The line number in the original source, or null.  The
- *     line number is 1-based.
- *   - column: The column number in the original source, or null.  The
- *     column number is 0-based.
- *   - name: The original identifier, or null.
- */
-IndexedSourceMapConsumer.prototype.originalPositionFor =
-  function IndexedSourceMapConsumer_originalPositionFor(aArgs) {
-    var needle = {
-      generatedLine: util.getArg(aArgs, 'line'),
-      generatedColumn: util.getArg(aArgs, 'column')
+  /**
+   * Returns the original source, line, and column information for the generated
+   * source's line and column positions provided. The only argument is an object
+   * with the following properties:
+   *
+   *   - line: The line number in the generated source.  The line number
+   *     is 1-based.
+   *   - column: The column number in the generated source.  The column
+   *     number is 0-based.
+   *
+   * and an object is returned with the following properties:
+   *
+   *   - source: The original source file, or null.
+   *   - line: The line number in the original source, or null.  The
+   *     line number is 1-based.
+   *   - column: The column number in the original source, or null.  The
+   *     column number is 0-based.
+   *   - name: The original identifier, or null.
+   */
+  originalPositionFor(aArgs) {
+    const needle = {
+      generatedLine: util.getArg(aArgs, "line"),
+      generatedColumn: util.getArg(aArgs, "column")
     };
 
     // Find the section containing the generated position we're trying to map
     // to an original position.
-    var sectionIndex = binarySearch.search(needle, this._sections,
-      function(needle, section) {
-        var cmp = needle.generatedLine - section.generatedOffset.generatedLine;
+    const sectionIndex = binarySearch.search(needle, this._sections,
+      function(aNeedle, section) {
+        const cmp = aNeedle.generatedLine - section.generatedOffset.generatedLine;
         if (cmp) {
           return cmp;
         }
 
-        return (needle.generatedColumn -
+        return (aNeedle.generatedColumn -
                 section.generatedOffset.generatedColumn);
       });
-    var section = this._sections[sectionIndex];
+    const section = this._sections[sectionIndex];
 
     if (!section) {
       return {
@@ -1003,30 +931,28 @@ IndexedSourceMapConsumer.prototype.originalPositionFor =
          : 0),
       bias: aArgs.bias
     });
-  };
+  }
 
-/**
- * Return true if we have the source content for every source in the source
- * map, false otherwise.
- */
-IndexedSourceMapConsumer.prototype.hasContentsOfAllSources =
-  function IndexedSourceMapConsumer_hasContentsOfAllSources() {
-    return this._sections.every(function (s) {
+  /**
+   * Return true if we have the source content for every source in the source
+   * map, false otherwise.
+   */
+  hasContentsOfAllSources() {
+    return this._sections.every(function(s) {
       return s.consumer.hasContentsOfAllSources();
     });
-  };
+  }
 
-/**
- * Returns the original source content. The only argument is the url of the
- * original source file. Returns null if no original source content is
- * available.
- */
-IndexedSourceMapConsumer.prototype.sourceContentFor =
-  function IndexedSourceMapConsumer_sourceContentFor(aSource, nullOnMissing) {
-    for (var i = 0; i < this._sections.length; i++) {
-      var section = this._sections[i];
+  /**
+   * Returns the original source content. The only argument is the url of the
+   * original source file. Returns null if no original source content is
+   * available.
+   */
+  sourceContentFor(aSource, nullOnMissing) {
+    for (let i = 0; i < this._sections.length; i++) {
+      const section = this._sections[i];
 
-      var content = section.consumer.sourceContentFor(aSource, true);
+      const content = section.consumer.sourceContentFor(aSource, true);
       if (content) {
         return content;
       }
@@ -1034,42 +960,39 @@ IndexedSourceMapConsumer.prototype.sourceContentFor =
     if (nullOnMissing) {
       return null;
     }
-    else {
-      throw new Error('"' + aSource + '" is not in the SourceMap.');
-    }
-  };
+    throw new Error('"' + aSource + '" is not in the SourceMap.');
+  }
 
-/**
- * Returns the generated line and column information for the original source,
- * line, and column positions provided. The only argument is an object with
- * the following properties:
- *
- *   - source: The filename of the original source.
- *   - line: The line number in the original source.  The line number
- *     is 1-based.
- *   - column: The column number in the original source.  The column
- *     number is 0-based.
- *
- * and an object is returned with the following properties:
- *
- *   - line: The line number in the generated source, or null.  The
- *     line number is 1-based. 
- *   - column: The column number in the generated source, or null.
- *     The column number is 0-based.
- */
-IndexedSourceMapConsumer.prototype.generatedPositionFor =
-  function IndexedSourceMapConsumer_generatedPositionFor(aArgs) {
-    for (var i = 0; i < this._sections.length; i++) {
-      var section = this._sections[i];
+  /**
+   * Returns the generated line and column information for the original source,
+   * line, and column positions provided. The only argument is an object with
+   * the following properties:
+   *
+   *   - source: The filename of the original source.
+   *   - line: The line number in the original source.  The line number
+   *     is 1-based.
+   *   - column: The column number in the original source.  The column
+   *     number is 0-based.
+   *
+   * and an object is returned with the following properties:
+   *
+   *   - line: The line number in the generated source, or null.  The
+   *     line number is 1-based.
+   *   - column: The column number in the generated source, or null.
+   *     The column number is 0-based.
+   */
+  generatedPositionFor(aArgs) {
+    for (let i = 0; i < this._sections.length; i++) {
+      const section = this._sections[i];
 
       // Only consider this section if the requested source is in the list of
       // sources of the consumer.
-      if (section.consumer._findSourceIndex(util.getArg(aArgs, 'source')) === -1) {
+      if (section.consumer._findSourceIndex(util.getArg(aArgs, "source")) === -1) {
         continue;
       }
-      var generatedPosition = section.consumer.generatedPositionFor(aArgs);
+      const generatedPosition = section.consumer.generatedPositionFor(aArgs);
       if (generatedPosition) {
-        var ret = {
+        const ret = {
           line: generatedPosition.line +
             (section.generatedOffset.generatedLine - 1),
           column: generatedPosition.column +
@@ -1085,41 +1008,45 @@ IndexedSourceMapConsumer.prototype.generatedPositionFor =
       line: null,
       column: null
     };
-  };
+  }
 
-/**
- * Parse the mappings in a string in to a data structure which we can easily
- * query (the ordered arrays in the `this.__generatedMappings` and
- * `this.__originalMappings` properties).
- */
-IndexedSourceMapConsumer.prototype._parseMappings =
-  function IndexedSourceMapConsumer_parseMappings(aStr, aSourceRoot) {
-    this.__generatedMappings = [];
-    this.__originalMappings = [];
-    for (var i = 0; i < this._sections.length; i++) {
-      var section = this._sections[i];
-      var sectionMappings = section.consumer._generatedMappings;
-      for (var j = 0; j < sectionMappings.length; j++) {
-        var mapping = sectionMappings[j];
-
-        var source = section.consumer._sources.at(mapping.source);
-        source = util.computeSourceURL(section.consumer.sourceRoot, source, this._sourceMapURL);
+  /**
+   * Parse the mappings in a string in to a data structure which we can easily
+   * query (the ordered arrays in the `this.__generatedMappings` and
+   * `this.__originalMappings` properties).
+   */
+  _parseMappings(aStr, aSourceRoot) {
+    const generatedMappings = this.__generatedMappingsUnsorted = [];
+    const originalMappings = this.__originalMappingsUnsorted = [];
+    for (let i = 0; i < this._sections.length; i++) {
+      const section = this._sections[i];
+
+      const sectionMappings = [];
+      section.consumer.eachMapping(m => sectionMappings.push(m));
+
+      for (let j = 0; j < sectionMappings.length; j++) {
+        const mapping = sectionMappings[j];
+
+        // TODO: test if null is correct here.  The original code used
+        // `source`, which would actually have gotten used as null because
+        // var's get hoisted.
+        // See: https://github.com/mozilla/source-map/issues/333
+        let source = util.computeSourceURL(section.consumer.sourceRoot, null, this._sourceMapURL);
         this._sources.add(source);
         source = this._sources.indexOf(source);
 
-        var name = null;
+        let name = null;
         if (mapping.name) {
-          name = section.consumer._names.at(mapping.name);
-          this._names.add(name);
-          name = this._names.indexOf(name);
+          this._names.add(mapping.name);
+          name = this._names.indexOf(mapping.name);
         }
 
         // The mappings coming from the consumer for the section have
         // generated positions relative to the start of the section, so we
         // need to offset them to be relative to the start of the concatenated
         // generated file.
-        var adjustedMapping = {
-          source: source,
+        const adjustedMapping = {
+          source,
           generatedLine: mapping.generatedLine +
             (section.generatedOffset.generatedLine - 1),
           generatedColumn: mapping.generatedColumn +
@@ -1128,18 +1055,183 @@ IndexedSourceMapConsumer.prototype._parseMappings =
             : 0),
           originalLine: mapping.originalLine,
           originalColumn: mapping.originalColumn,
-          name: name
+          name
         };
 
-        this.__generatedMappings.push(adjustedMapping);
-        if (typeof adjustedMapping.originalLine === 'number') {
-          this.__originalMappings.push(adjustedMapping);
+        generatedMappings.push(adjustedMapping);
+        if (typeof adjustedMapping.originalLine === "number") {
+          originalMappings.push(adjustedMapping);
         }
       }
     }
+  }
 
-    quickSort(this.__generatedMappings, util.compareByGeneratedPositionsDeflated);
-    quickSort(this.__originalMappings, util.compareByOriginalPositions);
-  };
+  eachMapping(aCallback, aContext, aOrder) {
+    const context = aContext || null;
+    const order = aOrder || SourceMapConsumer.GENERATED_ORDER;
 
+    let mappings;
+    switch (order) {
+    case SourceMapConsumer.GENERATED_ORDER:
+      mappings = this._generatedMappings;
+      break;
+    case SourceMapConsumer.ORIGINAL_ORDER:
+      mappings = this._originalMappings;
+      break;
+    default:
+      throw new Error("Unknown order of iteration.");
+    }
+
+    const sourceRoot = this.sourceRoot;
+    mappings.map(function(mapping) {
+      let source = null;
+      if (mapping.source !== null) {
+        source = this._sources.at(mapping.source);
+        source = util.computeSourceURL(sourceRoot, source, this._sourceMapURL);
+      }
+      return {
+        source,
+        generatedLine: mapping.generatedLine,
+        generatedColumn: mapping.generatedColumn,
+        originalLine: mapping.originalLine,
+        originalColumn: mapping.originalColumn,
+        name: mapping.name === null ? null : this._names.at(mapping.name)
+      };
+    }, this).forEach(aCallback, context);
+  }
+
+  /**
+   * Find the mapping that best matches the hypothetical "needle" mapping that
+   * we are searching for in the given "haystack" of mappings.
+   */
+  _findMapping(aNeedle, aMappings, aLineName,
+              aColumnName, aComparator, aBias) {
+    // To return the position we are searching for, we must first find the
+    // mapping for the given position and then return the opposite position it
+    // points to. Because the mappings are sorted, we can use binary search to
+    // find the best mapping.
+
+    if (aNeedle[aLineName] <= 0) {
+      throw new TypeError("Line must be greater than or equal to 1, got "
+                          + aNeedle[aLineName]);
+    }
+    if (aNeedle[aColumnName] < 0) {
+      throw new TypeError("Column must be greater than or equal to 0, got "
+                          + aNeedle[aColumnName]);
+    }
+
+    return binarySearch.search(aNeedle, aMappings, aComparator, aBias);
+  }
+
+  allGeneratedPositionsFor(aArgs) {
+    const line = util.getArg(aArgs, "line");
+
+    // When there is no exact match, BasicSourceMapConsumer.prototype._findMapping
+    // returns the index of the closest mapping less than the needle. By
+    // setting needle.originalColumn to 0, we thus find the last mapping for
+    // the given line, provided such a mapping exists.
+    const needle = {
+      source: util.getArg(aArgs, "source"),
+      originalLine: line,
+      originalColumn: util.getArg(aArgs, "column", 0)
+    };
+
+    needle.source = this._findSourceIndex(needle.source);
+    if (needle.source < 0) {
+      return [];
+    }
+
+    if (needle.originalLine < 1) {
+      throw new Error("Line numbers must be >= 1");
+    }
+
+    if (needle.originalColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
+    }
+
+    const mappings = [];
+
+    let index = this._findMapping(needle,
+                                  this._originalMappings,
+                                  "originalLine",
+                                  "originalColumn",
+                                  util.compareByOriginalPositions,
+                                  binarySearch.LEAST_UPPER_BOUND);
+    if (index >= 0) {
+      let mapping = this._originalMappings[index];
+
+      if (aArgs.column === undefined) {
+        const originalLine = mapping.originalLine;
+
+        // Iterate until either we run out of mappings, or we run into
+        // a mapping for a different line than the one we found. Since
+        // mappings are sorted, this is guaranteed to find all mappings for
+        // the line we found.
+        while (mapping && mapping.originalLine === originalLine) {
+          let lastColumn = mapping.lastGeneratedColumn;
+          if (this._computedColumnSpans && lastColumn === null) {
+            lastColumn = Infinity;
+          }
+          mappings.push({
+            line: util.getArg(mapping, "generatedLine", null),
+            column: util.getArg(mapping, "generatedColumn", null),
+            lastColumn,
+          });
+
+          mapping = this._originalMappings[++index];
+        }
+      } else {
+        const originalColumn = mapping.originalColumn;
+
+        // Iterate until either we run out of mappings, or we run into
+        // a mapping for a different line than the one we were searching for.
+        // Since mappings are sorted, this is guaranteed to find all mappings for
+        // the line we are searching for.
+        while (mapping &&
+               mapping.originalLine === line &&
+               mapping.originalColumn == originalColumn) {
+          let lastColumn = mapping.lastGeneratedColumn;
+          if (this._computedColumnSpans && lastColumn === null) {
+            lastColumn = Infinity;
+          }
+          mappings.push({
+            line: util.getArg(mapping, "generatedLine", null),
+            column: util.getArg(mapping, "generatedColumn", null),
+            lastColumn,
+          });
+
+          mapping = this._originalMappings[++index];
+        }
+      }
+    }
+
+    return mappings;
+  }
+
+  destroy() {
+    for (let i = 0; i < this._sections.length; i++) {
+      this._sections[i].consumer.destroy();
+    }
+  }
+}
 exports.IndexedSourceMapConsumer = IndexedSourceMapConsumer;
+
+/*
+ * Cheat to get around inter-twingled classes.  `factory()` can be at the end
+ * where it has access to non-hoisted classes, but it gets hoisted itself.
+ */
+function _factory(aSourceMap, aSourceMapURL) {
+  let sourceMap = aSourceMap;
+  if (typeof aSourceMap === "string") {
+    sourceMap = util.parseSourceMapInput(aSourceMap);
+  }
+
+  const consumer = sourceMap.sections != null
+      ? new IndexedSourceMapConsumer(sourceMap, aSourceMapURL)
+      : new BasicSourceMapConsumer(sourceMap, aSourceMapURL);
+  return Promise.resolve(consumer);
+}
+
+function _factoryBSM(aSourceMap, aSourceMapURL) {
+  return BasicSourceMapConsumer.fromSourceMap(aSourceMap, aSourceMapURL);
+}
diff --git a/node_modules/source-map/lib/source-map-generator.js b/node_modules/source-map/lib/source-map-generator.js
index 508bcfbb..8111e061 100644
--- a/node_modules/source-map/lib/source-map-generator.js
+++ b/node_modules/source-map/lib/source-map-generator.js
@@ -5,10 +5,10 @@
  * http://opensource.org/licenses/BSD-3-Clause
  */
 
-var base64VLQ = require('./base64-vlq');
-var util = require('./util');
-var ArraySet = require('./array-set').ArraySet;
-var MappingList = require('./mapping-list').MappingList;
+const base64VLQ = require("./base64-vlq");
+const util = require("./util");
+const ArraySet = require("./array-set").ArraySet;
+const MappingList = require("./mapping-list").MappingList;
 
 /**
  * An instance of the SourceMapGenerator represents a source map which is
@@ -18,35 +18,33 @@ var MappingList = require('./mapping-list').MappingList;
  *   - file: The filename of the generated source.
  *   - sourceRoot: A root for all relative URLs in this source map.
  */
-function SourceMapGenerator(aArgs) {
-  if (!aArgs) {
-    aArgs = {};
+class SourceMapGenerator {
+  constructor(aArgs) {
+    if (!aArgs) {
+      aArgs = {};
+    }
+    this._file = util.getArg(aArgs, "file", null);
+    this._sourceRoot = util.getArg(aArgs, "sourceRoot", null);
+    this._skipValidation = util.getArg(aArgs, "skipValidation", false);
+    this._sources = new ArraySet();
+    this._names = new ArraySet();
+    this._mappings = new MappingList();
+    this._sourcesContents = null;
   }
-  this._file = util.getArg(aArgs, 'file', null);
-  this._sourceRoot = util.getArg(aArgs, 'sourceRoot', null);
-  this._skipValidation = util.getArg(aArgs, 'skipValidation', false);
-  this._sources = new ArraySet();
-  this._names = new ArraySet();
-  this._mappings = new MappingList();
-  this._sourcesContents = null;
-}
-
-SourceMapGenerator.prototype._version = 3;
 
-/**
- * Creates a new SourceMapGenerator based on a SourceMapConsumer
- *
- * @param aSourceMapConsumer The SourceMap.
- */
-SourceMapGenerator.fromSourceMap =
-  function SourceMapGenerator_fromSourceMap(aSourceMapConsumer) {
-    var sourceRoot = aSourceMapConsumer.sourceRoot;
-    var generator = new SourceMapGenerator({
+  /**
+   * Creates a new SourceMapGenerator based on a SourceMapConsumer
+   *
+   * @param aSourceMapConsumer The SourceMap.
+   */
+  static fromSourceMap(aSourceMapConsumer) {
+    const sourceRoot = aSourceMapConsumer.sourceRoot;
+    const generator = new SourceMapGenerator({
       file: aSourceMapConsumer.file,
-      sourceRoot: sourceRoot
+      sourceRoot
     });
-    aSourceMapConsumer.eachMapping(function (mapping) {
-      var newMapping = {
+    aSourceMapConsumer.eachMapping(function(mapping) {
+      const newMapping = {
         generated: {
           line: mapping.generatedLine,
           column: mapping.generatedColumn
@@ -71,8 +69,8 @@ SourceMapGenerator.fromSourceMap =
 
       generator.addMapping(newMapping);
     });
-    aSourceMapConsumer.sources.forEach(function (sourceFile) {
-      var sourceRelative = sourceFile;
+    aSourceMapConsumer.sources.forEach(function(sourceFile) {
+      let sourceRelative = sourceFile;
       if (sourceRoot !== null) {
         sourceRelative = util.relative(sourceRoot, sourceFile);
       }
@@ -81,30 +79,29 @@ SourceMapGenerator.fromSourceMap =
         generator._sources.add(sourceRelative);
       }
 
-      var content = aSourceMapConsumer.sourceContentFor(sourceFile);
+      const content = aSourceMapConsumer.sourceContentFor(sourceFile);
       if (content != null) {
         generator.setSourceContent(sourceFile, content);
       }
     });
     return generator;
-  };
+  }
 
-/**
- * Add a single mapping from original source line and column to the generated
- * source's line and column for this source map being created. The mapping
- * object should have the following properties:
- *
- *   - generated: An object with the generated line and column positions.
- *   - original: An object with the original line and column positions.
- *   - source: The original source file (relative to the sourceRoot).
- *   - name: An optional original token name for this mapping.
- */
-SourceMapGenerator.prototype.addMapping =
-  function SourceMapGenerator_addMapping(aArgs) {
-    var generated = util.getArg(aArgs, 'generated');
-    var original = util.getArg(aArgs, 'original', null);
-    var source = util.getArg(aArgs, 'source', null);
-    var name = util.getArg(aArgs, 'name', null);
+  /**
+   * Add a single mapping from original source line and column to the generated
+   * source's line and column for this source map being created. The mapping
+   * object should have the following properties:
+   *
+   *   - generated: An object with the generated line and column positions.
+   *   - original: An object with the original line and column positions.
+   *   - source: The original source file (relative to the sourceRoot).
+   *   - name: An optional original token name for this mapping.
+   */
+  addMapping(aArgs) {
+    const generated = util.getArg(aArgs, "generated");
+    const original = util.getArg(aArgs, "original", null);
+    let source = util.getArg(aArgs, "source", null);
+    let name = util.getArg(aArgs, "name", null);
 
     if (!this._skipValidation) {
       this._validateMapping(generated, original, source, name);
@@ -129,17 +126,16 @@ SourceMapGenerator.prototype.addMapping =
       generatedColumn: generated.column,
       originalLine: original != null && original.line,
       originalColumn: original != null && original.column,
-      source: source,
-      name: name
+      source,
+      name
     });
-  };
+  }
 
-/**
- * Set the source content for a source file.
- */
-SourceMapGenerator.prototype.setSourceContent =
-  function SourceMapGenerator_setSourceContent(aSourceFile, aSourceContent) {
-    var source = aSourceFile;
+  /**
+   * Set the source content for a source file.
+   */
+  setSourceContent(aSourceFile, aSourceContent) {
+    let source = aSourceFile;
     if (this._sourceRoot != null) {
       source = util.relative(this._sourceRoot, source);
     }
@@ -159,52 +155,53 @@ SourceMapGenerator.prototype.setSourceContent =
         this._sourcesContents = null;
       }
     }
-  };
+  }
 
-/**
- * Applies the mappings of a sub-source-map for a specific source file to the
- * source map being generated. Each mapping to the supplied source file is
- * rewritten using the supplied source map. Note: The resolution for the
- * resulting mappings is the minimium of this map and the supplied map.
- *
- * @param aSourceMapConsumer The source map to be applied.
- * @param aSourceFile Optional. The filename of the source file.
- *        If omitted, SourceMapConsumer's file property will be used.
- * @param aSourceMapPath Optional. The dirname of the path to the source map
- *        to be applied. If relative, it is relative to the SourceMapConsumer.
- *        This parameter is needed when the two source maps aren't in the same
- *        directory, and the source map to be applied contains relative source
- *        paths. If so, those relative source paths need to be rewritten
- *        relative to the SourceMapGenerator.
- */
-SourceMapGenerator.prototype.applySourceMap =
-  function SourceMapGenerator_applySourceMap(aSourceMapConsumer, aSourceFile, aSourceMapPath) {
-    var sourceFile = aSourceFile;
+  /**
+   * Applies the mappings of a sub-source-map for a specific source file to the
+   * source map being generated. Each mapping to the supplied source file is
+   * rewritten using the supplied source map. Note: The resolution for the
+   * resulting mappings is the minimium of this map and the supplied map.
+   *
+   * @param aSourceMapConsumer The source map to be applied.
+   * @param aSourceFile Optional. The filename of the source file.
+   *        If omitted, SourceMapConsumer's file property will be used.
+   * @param aSourceMapPath Optional. The dirname of the path to the source map
+   *        to be applied. If relative, it is relative to the SourceMapConsumer.
+   *        This parameter is needed when the two source maps aren't in the same
+   *        directory, and the source map to be applied contains relative source
+   *        paths. If so, those relative source paths need to be rewritten
+   *        relative to the SourceMapGenerator.
+   */
+  applySourceMap(aSourceMapConsumer, aSourceFile, aSourceMapPath) {
+    let sourceFile = aSourceFile;
     // If aSourceFile is omitted, we will use the file property of the SourceMap
     if (aSourceFile == null) {
       if (aSourceMapConsumer.file == null) {
         throw new Error(
-          'SourceMapGenerator.prototype.applySourceMap requires either an explicit source file, ' +
+          "SourceMapGenerator.prototype.applySourceMap requires either an explicit source file, " +
           'or the source map\'s "file" property. Both were omitted.'
         );
       }
       sourceFile = aSourceMapConsumer.file;
     }
-    var sourceRoot = this._sourceRoot;
+    const sourceRoot = this._sourceRoot;
     // Make "sourceFile" relative if an absolute Url is passed.
     if (sourceRoot != null) {
       sourceFile = util.relative(sourceRoot, sourceFile);
     }
     // Applying the SourceMap can add and remove items from the sources and
     // the names array.
-    var newSources = new ArraySet();
-    var newNames = new ArraySet();
+    const newSources = this._mappings.toArray().length > 0
+      ? new ArraySet()
+      : this._sources;
+    const newNames = new ArraySet();
 
     // Find mappings for the "sourceFile"
-    this._mappings.unsortedForEach(function (mapping) {
+    this._mappings.unsortedForEach(function(mapping) {
       if (mapping.source === sourceFile && mapping.originalLine != null) {
         // Check if it can be mapped by the source map, then update the mapping.
-        var original = aSourceMapConsumer.originalPositionFor({
+        const original = aSourceMapConsumer.originalPositionFor({
           line: mapping.originalLine,
           column: mapping.originalColumn
         });
@@ -212,7 +209,7 @@ SourceMapGenerator.prototype.applySourceMap =
           // Copy mapping
           mapping.source = original.source;
           if (aSourceMapPath != null) {
-            mapping.source = util.join(aSourceMapPath, mapping.source)
+            mapping.source = util.join(aSourceMapPath, mapping.source);
           }
           if (sourceRoot != null) {
             mapping.source = util.relative(sourceRoot, mapping.source);
@@ -225,12 +222,12 @@ SourceMapGenerator.prototype.applySourceMap =
         }
       }
 
-      var source = mapping.source;
+      const source = mapping.source;
       if (source != null && !newSources.has(source)) {
         newSources.add(source);
       }
 
-      var name = mapping.name;
+      const name = mapping.name;
       if (name != null && !newNames.has(name)) {
         newNames.add(name);
       }
@@ -240,107 +237,99 @@ SourceMapGenerator.prototype.applySourceMap =
     this._names = newNames;
 
     // Copy sourcesContents of applied map.
-    aSourceMapConsumer.sources.forEach(function (sourceFile) {
-      var content = aSourceMapConsumer.sourceContentFor(sourceFile);
+    aSourceMapConsumer.sources.forEach(function(srcFile) {
+      const content = aSourceMapConsumer.sourceContentFor(srcFile);
       if (content != null) {
         if (aSourceMapPath != null) {
-          sourceFile = util.join(aSourceMapPath, sourceFile);
+          srcFile = util.join(aSourceMapPath, srcFile);
         }
         if (sourceRoot != null) {
-          sourceFile = util.relative(sourceRoot, sourceFile);
+          srcFile = util.relative(sourceRoot, srcFile);
         }
-        this.setSourceContent(sourceFile, content);
+        this.setSourceContent(srcFile, content);
       }
     }, this);
-  };
+  }
 
-/**
- * A mapping can have one of the three levels of data:
- *
- *   1. Just the generated position.
- *   2. The Generated position, original position, and original source.
- *   3. Generated and original position, original source, as well as a name
- *      token.
- *
- * To maintain consistency, we validate that any new mapping being added falls
- * in to one of these categories.
- */
-SourceMapGenerator.prototype._validateMapping =
-  function SourceMapGenerator_validateMapping(aGenerated, aOriginal, aSource,
-                                              aName) {
+  /**
+   * A mapping can have one of the three levels of data:
+   *
+   *   1. Just the generated position.
+   *   2. The Generated position, original position, and original source.
+   *   3. Generated and original position, original source, as well as a name
+   *      token.
+   *
+   * To maintain consistency, we validate that any new mapping being added falls
+   * in to one of these categories.
+   */
+  _validateMapping(aGenerated, aOriginal, aSource, aName) {
     // When aOriginal is truthy but has empty values for .line and .column,
     // it is most likely a programmer error. In this case we throw a very
     // specific error message to try to guide them the right way.
     // For example: https://github.com/Polymer/polymer-bundler/pull/519
-    if (aOriginal && typeof aOriginal.line !== 'number' && typeof aOriginal.column !== 'number') {
+    if (aOriginal && typeof aOriginal.line !== "number" && typeof aOriginal.column !== "number") {
         throw new Error(
-            'original.line and original.column are not numbers -- you probably meant to omit ' +
-            'the original mapping entirely and only map the generated position. If so, pass ' +
-            'null for the original mapping instead of an object with empty or null values.'
+            "original.line and original.column are not numbers -- you probably meant to omit " +
+            "the original mapping entirely and only map the generated position. If so, pass " +
+            "null for the original mapping instead of an object with empty or null values."
         );
     }
 
-    if (aGenerated && 'line' in aGenerated && 'column' in aGenerated
+    if (aGenerated && "line" in aGenerated && "column" in aGenerated
         && aGenerated.line > 0 && aGenerated.column >= 0
         && !aOriginal && !aSource && !aName) {
       // Case 1.
-      return;
-    }
-    else if (aGenerated && 'line' in aGenerated && 'column' in aGenerated
-             && aOriginal && 'line' in aOriginal && 'column' in aOriginal
+
+    } else if (aGenerated && "line" in aGenerated && "column" in aGenerated
+             && aOriginal && "line" in aOriginal && "column" in aOriginal
              && aGenerated.line > 0 && aGenerated.column >= 0
              && aOriginal.line > 0 && aOriginal.column >= 0
              && aSource) {
       // Cases 2 and 3.
-      return;
-    }
-    else {
-      throw new Error('Invalid mapping: ' + JSON.stringify({
+
+    } else {
+      throw new Error("Invalid mapping: " + JSON.stringify({
         generated: aGenerated,
         source: aSource,
         original: aOriginal,
         name: aName
       }));
     }
-  };
+  }
 
-/**
- * Serialize the accumulated mappings in to the stream of base 64 VLQs
- * specified by the source map format.
- */
-SourceMapGenerator.prototype._serializeMappings =
-  function SourceMapGenerator_serializeMappings() {
-    var previousGeneratedColumn = 0;
-    var previousGeneratedLine = 1;
-    var previousOriginalColumn = 0;
-    var previousOriginalLine = 0;
-    var previousName = 0;
-    var previousSource = 0;
-    var result = '';
-    var next;
-    var mapping;
-    var nameIdx;
-    var sourceIdx;
-
-    var mappings = this._mappings.toArray();
-    for (var i = 0, len = mappings.length; i < len; i++) {
+  /**
+   * Serialize the accumulated mappings in to the stream of base 64 VLQs
+   * specified by the source map format.
+   */
+  _serializeMappings() {
+    let previousGeneratedColumn = 0;
+    let previousGeneratedLine = 1;
+    let previousOriginalColumn = 0;
+    let previousOriginalLine = 0;
+    let previousName = 0;
+    let previousSource = 0;
+    let result = "";
+    let next;
+    let mapping;
+    let nameIdx;
+    let sourceIdx;
+
+    const mappings = this._mappings.toArray();
+    for (let i = 0, len = mappings.length; i < len; i++) {
       mapping = mappings[i];
-      next = ''
+      next = "";
 
       if (mapping.generatedLine !== previousGeneratedLine) {
         previousGeneratedColumn = 0;
         while (mapping.generatedLine !== previousGeneratedLine) {
-          next += ';';
+          next += ";";
           previousGeneratedLine++;
         }
-      }
-      else {
-        if (i > 0) {
-          if (!util.compareByGeneratedPositionsInflated(mapping, mappings[i - 1])) {
-            continue;
-          }
-          next += ',';
+      } else if (i > 0) {
+        if (!util.compareByGeneratedPositionsInflated(mapping, mappings[i - 1])) {
+          continue;
         }
+        next += ",";
       }
 
       next += base64VLQ.encode(mapping.generatedColumn
@@ -372,30 +361,28 @@ SourceMapGenerator.prototype._serializeMappings =
     }
 
     return result;
-  };
+  }
 
-SourceMapGenerator.prototype._generateSourcesContent =
-  function SourceMapGenerator_generateSourcesContent(aSources, aSourceRoot) {
-    return aSources.map(function (source) {
+  _generateSourcesContent(aSources, aSourceRoot) {
+    return aSources.map(function(source) {
       if (!this._sourcesContents) {
         return null;
       }
       if (aSourceRoot != null) {
         source = util.relative(aSourceRoot, source);
       }
-      var key = util.toSetString(source);
+      const key = util.toSetString(source);
       return Object.prototype.hasOwnProperty.call(this._sourcesContents, key)
         ? this._sourcesContents[key]
         : null;
     }, this);
-  };
+  }
 
-/**
- * Externalize the source map.
- */
-SourceMapGenerator.prototype.toJSON =
-  function SourceMapGenerator_toJSON() {
-    var map = {
+  /**
+   * Externalize the source map.
+   */
+  toJSON() {
+    const map = {
       version: this._version,
       sources: this._sources.toArray(),
       names: this._names.toArray(),
@@ -412,14 +399,15 @@ SourceMapGenerator.prototype.toJSON =
     }
 
     return map;
-  };
+  }
 
-/**
- * Render the source map being generated to a string.
- */
-SourceMapGenerator.prototype.toString =
-  function SourceMapGenerator_toString() {
+  /**
+   * Render the source map being generated to a string.
+   */
+  toString() {
     return JSON.stringify(this.toJSON());
-  };
+  }
+}
 
+SourceMapGenerator.prototype._version = 3;
 exports.SourceMapGenerator = SourceMapGenerator;
diff --git a/node_modules/source-map/lib/source-node.js b/node_modules/source-map/lib/source-node.js
index 8bcdbe38..8a7a157e 100644
--- a/node_modules/source-map/lib/source-node.js
+++ b/node_modules/source-map/lib/source-node.js
@@ -5,20 +5,20 @@
  * http://opensource.org/licenses/BSD-3-Clause
  */
 
-var SourceMapGenerator = require('./source-map-generator').SourceMapGenerator;
-var util = require('./util');
+const SourceMapGenerator = require("./source-map-generator").SourceMapGenerator;
+const util = require("./util");
 
 // Matches a Windows-style `\r\n` newline or a `\n` newline used by all other
 // operating systems these days (capturing the result).
-var REGEX_NEWLINE = /(\r?\n)/;
+const REGEX_NEWLINE = /(\r?\n)/;
 
 // Newline character code for charCodeAt() comparisons
-var NEWLINE_CODE = 10;
+const NEWLINE_CODE = 10;
 
 // Private symbol for identifying `SourceNode`s when multiple versions of
 // the source-map library are loaded. This MUST NOT CHANGE across
 // versions!
-var isSourceNode = "$$$isSourceNode$$$";
+const isSourceNode = "$$$isSourceNode$$$";
 
 /**
  * SourceNodes provide a way to abstract over interpolating/concatenating
@@ -32,41 +32,41 @@ var isSourceNode = "$$$isSourceNode$$$";
  *        generated JS, or other SourceNodes.
  * @param aName The original identifier.
  */
-function SourceNode(aLine, aColumn, aSource, aChunks, aName) {
-  this.children = [];
-  this.sourceContents = {};
-  this.line = aLine == null ? null : aLine;
-  this.column = aColumn == null ? null : aColumn;
-  this.source = aSource == null ? null : aSource;
-  this.name = aName == null ? null : aName;
-  this[isSourceNode] = true;
-  if (aChunks != null) this.add(aChunks);
-}
+class SourceNode {
+  constructor(aLine, aColumn, aSource, aChunks, aName) {
+    this.children = [];
+    this.sourceContents = {};
+    this.line = aLine == null ? null : aLine;
+    this.column = aColumn == null ? null : aColumn;
+    this.source = aSource == null ? null : aSource;
+    this.name = aName == null ? null : aName;
+    this[isSourceNode] = true;
+    if (aChunks != null) this.add(aChunks);
+  }
 
-/**
- * Creates a SourceNode from generated code and a SourceMapConsumer.
- *
- * @param aGeneratedCode The generated code
- * @param aSourceMapConsumer The SourceMap for the generated code
- * @param aRelativePath Optional. The path that relative sources in the
- *        SourceMapConsumer should be relative to.
- */
-SourceNode.fromStringWithSourceMap =
-  function SourceNode_fromStringWithSourceMap(aGeneratedCode, aSourceMapConsumer, aRelativePath) {
+  /**
+   * Creates a SourceNode from generated code and a SourceMapConsumer.
+   *
+   * @param aGeneratedCode The generated code
+   * @param aSourceMapConsumer The SourceMap for the generated code
+   * @param aRelativePath Optional. The path that relative sources in the
+   *        SourceMapConsumer should be relative to.
+   */
+  static fromStringWithSourceMap(aGeneratedCode, aSourceMapConsumer, aRelativePath) {
     // The SourceNode we want to fill with the generated code
     // and the SourceMap
-    var node = new SourceNode();
+    const node = new SourceNode();
 
     // All even indices of this array are one line of the generated code,
     // while all odd indices are the newlines between two adjacent lines
     // (since `REGEX_NEWLINE` captures its match).
     // Processed fragments are accessed by calling `shiftNextLine`.
-    var remainingLines = aGeneratedCode.split(REGEX_NEWLINE);
-    var remainingLinesIndex = 0;
-    var shiftNextLine = function() {
-      var lineContents = getNextLine();
+    const remainingLines = aGeneratedCode.split(REGEX_NEWLINE);
+    let remainingLinesIndex = 0;
+    const shiftNextLine = function() {
+      const lineContents = getNextLine();
       // The last line of a file might not have a newline.
-      var newLine = getNextLine() || "";
+      const newLine = getNextLine() || "";
       return lineContents + newLine;
 
       function getNextLine() {
@@ -76,14 +76,15 @@ SourceNode.fromStringWithSourceMap =
     };
 
     // We need to remember the position of "remainingLines"
-    var lastGeneratedLine = 1, lastGeneratedColumn = 0;
+    let lastGeneratedLine = 1, lastGeneratedColumn = 0;
 
     // The generate SourceNodes we need a code range.
     // To extract it current and last mapping is used.
     // Here we store the last mapping.
-    var lastMapping = null;
+    let lastMapping = null;
+    let nextLine;
 
-    aSourceMapConsumer.eachMapping(function (mapping) {
+    aSourceMapConsumer.eachMapping(function(mapping) {
       if (lastMapping !== null) {
         // We add the code from "lastMapping" to "mapping":
         // First check if there is a new line in between.
@@ -97,8 +98,8 @@ SourceNode.fromStringWithSourceMap =
           // There is no new line in between.
           // Associate the code between "lastGeneratedColumn" and
           // "mapping.generatedColumn" with "lastMapping"
-          var nextLine = remainingLines[remainingLinesIndex] || '';
-          var code = nextLine.substr(0, mapping.generatedColumn -
+          nextLine = remainingLines[remainingLinesIndex] || "";
+          const code = nextLine.substr(0, mapping.generatedColumn -
                                         lastGeneratedColumn);
           remainingLines[remainingLinesIndex] = nextLine.substr(mapping.generatedColumn -
                                               lastGeneratedColumn);
@@ -117,7 +118,7 @@ SourceNode.fromStringWithSourceMap =
         lastGeneratedLine++;
       }
       if (lastGeneratedColumn < mapping.generatedColumn) {
-        var nextLine = remainingLines[remainingLinesIndex] || '';
+        nextLine = remainingLines[remainingLinesIndex] || "";
         node.add(nextLine.substr(0, mapping.generatedColumn));
         remainingLines[remainingLinesIndex] = nextLine.substr(mapping.generatedColumn);
         lastGeneratedColumn = mapping.generatedColumn;
@@ -135,8 +136,8 @@ SourceNode.fromStringWithSourceMap =
     }
 
     // Copy sourcesContent into SourceNode
-    aSourceMapConsumer.sources.forEach(function (sourceFile) {
-      var content = aSourceMapConsumer.sourceContentFor(sourceFile);
+    aSourceMapConsumer.sources.forEach(function(sourceFile) {
+      const content = aSourceMapConsumer.sourceContentFor(sourceFile);
       if (content != null) {
         if (aRelativePath != null) {
           sourceFile = util.join(aRelativePath, sourceFile);
@@ -151,7 +152,7 @@ SourceNode.fromStringWithSourceMap =
       if (mapping === null || mapping.source === undefined) {
         node.add(code);
       } else {
-        var source = aRelativePath
+        const source = aRelativePath
           ? util.join(aRelativePath, mapping.source)
           : mapping.source;
         node.add(new SourceNode(mapping.originalLine,
@@ -161,230 +162,182 @@ SourceNode.fromStringWithSourceMap =
                                 mapping.name));
       }
     }
-  };
-
-/**
- * Add a chunk of generated JS to this source node.
- *
- * @param aChunk A string snippet of generated JS code, another instance of
- *        SourceNode, or an array where each member is one of those things.
- */
-SourceNode.prototype.add = function SourceNode_add(aChunk) {
-  if (Array.isArray(aChunk)) {
-    aChunk.forEach(function (chunk) {
-      this.add(chunk);
-    }, this);
   }
-  else if (aChunk[isSourceNode] || typeof aChunk === "string") {
-    if (aChunk) {
-      this.children.push(aChunk);
+
+  /**
+   * Add a chunk of generated JS to this source node.
+   *
+   * @param aChunk A string snippet of generated JS code, another instance of
+   *        SourceNode, or an array where each member is one of those things.
+   */
+  add(aChunk) {
+    if (Array.isArray(aChunk)) {
+      aChunk.forEach(function(chunk) {
+        this.add(chunk);
+      }, this);
+    } else if (aChunk[isSourceNode] || typeof aChunk === "string") {
+      if (aChunk) {
+        this.children.push(aChunk);
+      }
+    } else {
+      throw new TypeError(
+        "Expected a SourceNode, string, or an array of SourceNodes and strings. Got " + aChunk
+      );
     }
+    return this;
   }
-  else {
-    throw new TypeError(
-      "Expected a SourceNode, string, or an array of SourceNodes and strings. Got " + aChunk
-    );
-  }
-  return this;
-};
 
-/**
- * Add a chunk of generated JS to the beginning of this source node.
- *
- * @param aChunk A string snippet of generated JS code, another instance of
- *        SourceNode, or an array where each member is one of those things.
- */
-SourceNode.prototype.prepend = function SourceNode_prepend(aChunk) {
-  if (Array.isArray(aChunk)) {
-    for (var i = aChunk.length-1; i >= 0; i--) {
-      this.prepend(aChunk[i]);
+  /**
+   * Add a chunk of generated JS to the beginning of this source node.
+   *
+   * @param aChunk A string snippet of generated JS code, another instance of
+   *        SourceNode, or an array where each member is one of those things.
+   */
+  prepend(aChunk) {
+    if (Array.isArray(aChunk)) {
+      for (let i = aChunk.length - 1; i >= 0; i--) {
+        this.prepend(aChunk[i]);
+      }
+    } else if (aChunk[isSourceNode] || typeof aChunk === "string") {
+      this.children.unshift(aChunk);
+    } else {
+      throw new TypeError(
+        "Expected a SourceNode, string, or an array of SourceNodes and strings. Got " + aChunk
+      );
     }
+    return this;
   }
-  else if (aChunk[isSourceNode] || typeof aChunk === "string") {
-    this.children.unshift(aChunk);
-  }
-  else {
-    throw new TypeError(
-      "Expected a SourceNode, string, or an array of SourceNodes and strings. Got " + aChunk
-    );
-  }
-  return this;
-};
 
-/**
- * Walk over the tree of JS snippets in this node and its children. The
- * walking function is called once for each snippet of JS and is passed that
- * snippet and the its original associated source's line/column location.
- *
- * @param aFn The traversal function.
- */
-SourceNode.prototype.walk = function SourceNode_walk(aFn) {
-  var chunk;
-  for (var i = 0, len = this.children.length; i < len; i++) {
-    chunk = this.children[i];
-    if (chunk[isSourceNode]) {
-      chunk.walk(aFn);
-    }
-    else {
-      if (chunk !== '') {
+  /**
+   * Walk over the tree of JS snippets in this node and its children. The
+   * walking function is called once for each snippet of JS and is passed that
+   * snippet and the its original associated source's line/column location.
+   *
+   * @param aFn The traversal function.
+   */
+  walk(aFn) {
+    let chunk;
+    for (let i = 0, len = this.children.length; i < len; i++) {
+      chunk = this.children[i];
+      if (chunk[isSourceNode]) {
+        chunk.walk(aFn);
+      } else if (chunk !== "") {
         aFn(chunk, { source: this.source,
-                     line: this.line,
-                     column: this.column,
-                     name: this.name });
+                      line: this.line,
+                      column: this.column,
+                      name: this.name });
       }
     }
   }
-};
 
-/**
- * Like `String.prototype.join` except for SourceNodes. Inserts `aStr` between
- * each of `this.children`.
- *
- * @param aSep The separator.
- */
-SourceNode.prototype.join = function SourceNode_join(aSep) {
-  var newChildren;
-  var i;
-  var len = this.children.length;
-  if (len > 0) {
-    newChildren = [];
-    for (i = 0; i < len-1; i++) {
+  /**
+   * Like `String.prototype.join` except for SourceNodes. Inserts `aStr` between
+   * each of `this.children`.
+   *
+   * @param aSep The separator.
+   */
+  join(aSep) {
+    let newChildren;
+    let i;
+    const len = this.children.length;
+    if (len > 0) {
+      newChildren = [];
+      for (i = 0; i < len - 1; i++) {
+        newChildren.push(this.children[i]);
+        newChildren.push(aSep);
+      }
       newChildren.push(this.children[i]);
-      newChildren.push(aSep);
+      this.children = newChildren;
     }
-    newChildren.push(this.children[i]);
-    this.children = newChildren;
+    return this;
   }
-  return this;
-};
 
-/**
- * Call String.prototype.replace on the very right-most source snippet. Useful
- * for trimming whitespace from the end of a source node, etc.
- *
- * @param aPattern The pattern to replace.
- * @param aReplacement The thing to replace the pattern with.
- */
-SourceNode.prototype.replaceRight = function SourceNode_replaceRight(aPattern, aReplacement) {
-  var lastChild = this.children[this.children.length - 1];
-  if (lastChild[isSourceNode]) {
-    lastChild.replaceRight(aPattern, aReplacement);
-  }
-  else if (typeof lastChild === 'string') {
-    this.children[this.children.length - 1] = lastChild.replace(aPattern, aReplacement);
-  }
-  else {
-    this.children.push(''.replace(aPattern, aReplacement));
+  /**
+   * Call String.prototype.replace on the very right-most source snippet. Useful
+   * for trimming whitespace from the end of a source node, etc.
+   *
+   * @param aPattern The pattern to replace.
+   * @param aReplacement The thing to replace the pattern with.
+   */
+  replaceRight(aPattern, aReplacement) {
+    const lastChild = this.children[this.children.length - 1];
+    if (lastChild[isSourceNode]) {
+      lastChild.replaceRight(aPattern, aReplacement);
+    } else if (typeof lastChild === "string") {
+      this.children[this.children.length - 1] = lastChild.replace(aPattern, aReplacement);
+    } else {
+      this.children.push("".replace(aPattern, aReplacement));
+    }
+    return this;
   }
-  return this;
-};
 
-/**
- * Set the source content for a source file. This will be added to the SourceMapGenerator
- * in the sourcesContent field.
- *
- * @param aSourceFile The filename of the source file
- * @param aSourceContent The content of the source file
- */
-SourceNode.prototype.setSourceContent =
-  function SourceNode_setSourceContent(aSourceFile, aSourceContent) {
+  /**
+   * Set the source content for a source file. This will be added to the SourceMapGenerator
+   * in the sourcesContent field.
+   *
+   * @param aSourceFile The filename of the source file
+   * @param aSourceContent The content of the source file
+   */
+  setSourceContent(aSourceFile, aSourceContent) {
     this.sourceContents[util.toSetString(aSourceFile)] = aSourceContent;
-  };
+  }
 
-/**
- * Walk over the tree of SourceNodes. The walking function is called for each
- * source file content and is passed the filename and source content.
- *
- * @param aFn The traversal function.
- */
-SourceNode.prototype.walkSourceContents =
-  function SourceNode_walkSourceContents(aFn) {
-    for (var i = 0, len = this.children.length; i < len; i++) {
+  /**
+   * Walk over the tree of SourceNodes. The walking function is called for each
+   * source file content and is passed the filename and source content.
+   *
+   * @param aFn The traversal function.
+   */
+  walkSourceContents(aFn) {
+    for (let i = 0, len = this.children.length; i < len; i++) {
       if (this.children[i][isSourceNode]) {
         this.children[i].walkSourceContents(aFn);
       }
     }
 
-    var sources = Object.keys(this.sourceContents);
-    for (var i = 0, len = sources.length; i < len; i++) {
+    const sources = Object.keys(this.sourceContents);
+    for (let i = 0, len = sources.length; i < len; i++) {
       aFn(util.fromSetString(sources[i]), this.sourceContents[sources[i]]);
     }
-  };
+  }
 
-/**
- * Return the string representation of this source node. Walks over the tree
- * and concatenates all the various snippets together to one string.
- */
-SourceNode.prototype.toString = function SourceNode_toString() {
-  var str = "";
-  this.walk(function (chunk) {
-    str += chunk;
-  });
-  return str;
-};
+  /**
+   * Return the string representation of this source node. Walks over the tree
+   * and concatenates all the various snippets together to one string.
+   */
+  toString() {
+    let str = "";
+    this.walk(function(chunk) {
+      str += chunk;
+    });
+    return str;
+  }
 
-/**
- * Returns the string representation of this source node along with a source
- * map.
- */
-SourceNode.prototype.toStringWithSourceMap = function SourceNode_toStringWithSourceMap(aArgs) {
-  var generated = {
-    code: "",
-    line: 1,
-    column: 0
-  };
-  var map = new SourceMapGenerator(aArgs);
-  var sourceMappingActive = false;
-  var lastOriginalSource = null;
-  var lastOriginalLine = null;
-  var lastOriginalColumn = null;
-  var lastOriginalName = null;
-  this.walk(function (chunk, original) {
-    generated.code += chunk;
-    if (original.source !== null
-        && original.line !== null
-        && original.column !== null) {
-      if(lastOriginalSource !== original.source
-         || lastOriginalLine !== original.line
-         || lastOriginalColumn !== original.column
-         || lastOriginalName !== original.name) {
-        map.addMapping({
-          source: original.source,
-          original: {
-            line: original.line,
-            column: original.column
-          },
-          generated: {
-            line: generated.line,
-            column: generated.column
-          },
-          name: original.name
-        });
-      }
-      lastOriginalSource = original.source;
-      lastOriginalLine = original.line;
-      lastOriginalColumn = original.column;
-      lastOriginalName = original.name;
-      sourceMappingActive = true;
-    } else if (sourceMappingActive) {
-      map.addMapping({
-        generated: {
-          line: generated.line,
-          column: generated.column
-        }
-      });
-      lastOriginalSource = null;
-      sourceMappingActive = false;
-    }
-    for (var idx = 0, length = chunk.length; idx < length; idx++) {
-      if (chunk.charCodeAt(idx) === NEWLINE_CODE) {
-        generated.line++;
-        generated.column = 0;
-        // Mappings end at eol
-        if (idx + 1 === length) {
-          lastOriginalSource = null;
-          sourceMappingActive = false;
-        } else if (sourceMappingActive) {
+  /**
+   * Returns the string representation of this source node along with a source
+   * map.
+   */
+  toStringWithSourceMap(aArgs) {
+    const generated = {
+      code: "",
+      line: 1,
+      column: 0
+    };
+    const map = new SourceMapGenerator(aArgs);
+    let sourceMappingActive = false;
+    let lastOriginalSource = null;
+    let lastOriginalLine = null;
+    let lastOriginalColumn = null;
+    let lastOriginalName = null;
+    this.walk(function(chunk, original) {
+      generated.code += chunk;
+      if (original.source !== null
+          && original.line !== null
+          && original.column !== null) {
+        if (lastOriginalSource !== original.source
+          || lastOriginalLine !== original.line
+          || lastOriginalColumn !== original.column
+          || lastOriginalName !== original.name) {
           map.addMapping({
             source: original.source,
             original: {
@@ -398,16 +351,54 @@ SourceNode.prototype.toStringWithSourceMap = function SourceNode_toStringWithSou
             name: original.name
           });
         }
-      } else {
-        generated.column++;
+        lastOriginalSource = original.source;
+        lastOriginalLine = original.line;
+        lastOriginalColumn = original.column;
+        lastOriginalName = original.name;
+        sourceMappingActive = true;
+      } else if (sourceMappingActive) {
+        map.addMapping({
+          generated: {
+            line: generated.line,
+            column: generated.column
+          }
+        });
+        lastOriginalSource = null;
+        sourceMappingActive = false;
       }
-    }
-  });
-  this.walkSourceContents(function (sourceFile, sourceContent) {
-    map.setSourceContent(sourceFile, sourceContent);
-  });
+      for (let idx = 0, length = chunk.length; idx < length; idx++) {
+        if (chunk.charCodeAt(idx) === NEWLINE_CODE) {
+          generated.line++;
+          generated.column = 0;
+          // Mappings end at eol
+          if (idx + 1 === length) {
+            lastOriginalSource = null;
+            sourceMappingActive = false;
+          } else if (sourceMappingActive) {
+            map.addMapping({
+              source: original.source,
+              original: {
+                line: original.line,
+                column: original.column
+              },
+              generated: {
+                line: generated.line,
+                column: generated.column
+              },
+              name: original.name
+            });
+          }
+        } else {
+          generated.column++;
+        }
+      }
+    });
+    this.walkSourceContents(function(sourceFile, sourceContent) {
+      map.setSourceContent(sourceFile, sourceContent);
+    });
 
-  return { code: generated.code, map: map };
-};
+    return { code: generated.code, map };
+  }
+}
 
 exports.SourceNode = SourceNode;
diff --git a/node_modules/source-map/lib/util.js b/node_modules/source-map/lib/util.js
index 3ca92e56..35bd93d6 100644
--- a/node_modules/source-map/lib/util.js
+++ b/node_modules/source-map/lib/util.js
@@ -20,17 +20,17 @@ function getArg(aArgs, aName, aDefaultValue) {
     return aArgs[aName];
   } else if (arguments.length === 3) {
     return aDefaultValue;
-  } else {
-    throw new Error('"' + aName + '" is a required argument.');
   }
+    throw new Error('"' + aName + '" is a required argument.');
+
 }
 exports.getArg = getArg;
 
-var urlRegexp = /^(?:([\w+\-.]+):)?\/\/(?:(\w+:\w+)@)?([\w.-]*)(?::(\d+))?(.*)$/;
-var dataUrlRegexp = /^data:.+\,.+$/;
+const urlRegexp = /^(?:([\w+\-.]+):)?\/\/(?:(\w+:\w+)@)?([\w.-]*)(?::(\d+))?(.*)$/;
+const dataUrlRegexp = /^data:.+\,.+$/;
 
 function urlParse(aUrl) {
-  var match = aUrl.match(urlRegexp);
+  const match = aUrl.match(urlRegexp);
   if (!match) {
     return null;
   }
@@ -45,19 +45,19 @@ function urlParse(aUrl) {
 exports.urlParse = urlParse;
 
 function urlGenerate(aParsedUrl) {
-  var url = '';
+  let url = "";
   if (aParsedUrl.scheme) {
-    url += aParsedUrl.scheme + ':';
+    url += aParsedUrl.scheme + ":";
   }
-  url += '//';
+  url += "//";
   if (aParsedUrl.auth) {
-    url += aParsedUrl.auth + '@';
+    url += aParsedUrl.auth + "@";
   }
   if (aParsedUrl.host) {
     url += aParsedUrl.host;
   }
   if (aParsedUrl.port) {
-    url += ":" + aParsedUrl.port
+    url += ":" + aParsedUrl.port;
   }
   if (aParsedUrl.path) {
     url += aParsedUrl.path;
@@ -66,6 +66,43 @@ function urlGenerate(aParsedUrl) {
 }
 exports.urlGenerate = urlGenerate;
 
+const MAX_CACHED_INPUTS = 32;
+
+/**
+ * Takes some function `f(input) -> result` and returns a memoized version of
+ * `f`.
+ *
+ * We keep at most `MAX_CACHED_INPUTS` memoized results of `f` alive. The
+ * memoization is a dumb-simple, linear least-recently-used cache.
+ */
+function lruMemoize(f) {
+  const cache = [];
+
+  return function(input) {
+    for (let i = 0; i < cache.length; i++) {
+      if (cache[i].input === input) {
+        const temp = cache[0];
+        cache[0] = cache[i];
+        cache[i] = temp;
+        return cache[0].result;
+      }
+    }
+
+    const result = f(input);
+
+    cache.unshift({
+      input,
+      result,
+    });
+
+    if (cache.length > MAX_CACHED_INPUTS) {
+      cache.pop();
+    }
+
+    return result;
+  };
+}
+
 /**
  * Normalizes a path, or the path portion of a URL:
  *
@@ -77,26 +114,45 @@ exports.urlGenerate = urlGenerate;
  *
  * @param aPath The path or url to normalize.
  */
-function normalize(aPath) {
-  var path = aPath;
-  var url = urlParse(aPath);
+const normalize = lruMemoize(function normalize(aPath) {
+  let path = aPath;
+  const url = urlParse(aPath);
   if (url) {
     if (!url.path) {
       return aPath;
     }
     path = url.path;
   }
-  var isAbsolute = exports.isAbsolute(path);
+  const isAbsolute = exports.isAbsolute(path);
+
+  // Split the path into parts between `/` characters. This is much faster than
+  // using `.split(/\/+/g)`.
+  const parts = [];
+  let start = 0;
+  let i = 0;
+  while (true) {
+    start = i;
+    i = path.indexOf("/", start);
+    if (i === -1) {
+      parts.push(path.slice(start));
+      break;
+    } else {
+      parts.push(path.slice(start, i));
+      while (i < path.length && path[i] === "/") {
+        i++;
+      }
+    }
+  }
 
-  var parts = path.split(/\/+/);
-  for (var part, up = 0, i = parts.length - 1; i >= 0; i--) {
-    part = parts[i];
-    if (part === '.') {
+  let up = 0;
+  for (i = parts.length - 1; i >= 0; i--) {
+    const part = parts[i];
+    if (part === ".") {
       parts.splice(i, 1);
-    } else if (part === '..') {
+    } else if (part === "..") {
       up++;
     } else if (up > 0) {
-      if (part === '') {
+      if (part === "") {
         // The first part is blank if the path is absolute. Trying to go
         // above the root is a no-op. Therefore we can remove all '..' parts
         // directly after the root.
@@ -108,10 +164,10 @@ function normalize(aPath) {
       }
     }
   }
-  path = parts.join('/');
+  path = parts.join("/");
 
-  if (path === '') {
-    path = isAbsolute ? '/' : '.';
+  if (path === "") {
+    path = isAbsolute ? "/" : ".";
   }
 
   if (url) {
@@ -119,7 +175,7 @@ function normalize(aPath) {
     return urlGenerate(url);
   }
   return path;
-}
+});
 exports.normalize = normalize;
 
 /**
@@ -145,10 +201,10 @@ function join(aRoot, aPath) {
   if (aPath === "") {
     aPath = ".";
   }
-  var aPathUrl = urlParse(aPath);
-  var aRootUrl = urlParse(aRoot);
+  const aPathUrl = urlParse(aPath);
+  const aRootUrl = urlParse(aRoot);
   if (aRootUrl) {
-    aRoot = aRootUrl.path || '/';
+    aRoot = aRootUrl.path || "/";
   }
 
   // `join(foo, '//www.example.org')`
@@ -169,9 +225,9 @@ function join(aRoot, aPath) {
     return urlGenerate(aRootUrl);
   }
 
-  var joined = aPath.charAt(0) === '/'
+  const joined = aPath.charAt(0) === "/"
     ? aPath
-    : normalize(aRoot.replace(/\/+$/, '') + '/' + aPath);
+    : normalize(aRoot.replace(/\/+$/, "") + "/" + aPath);
 
   if (aRootUrl) {
     aRootUrl.path = joined;
@@ -181,8 +237,8 @@ function join(aRoot, aPath) {
 }
 exports.join = join;
 
-exports.isAbsolute = function (aPath) {
-  return aPath.charAt(0) === '/' || urlRegexp.test(aPath);
+exports.isAbsolute = function(aPath) {
+  return aPath.charAt(0) === "/" || urlRegexp.test(aPath);
 };
 
 /**
@@ -196,15 +252,15 @@ function relative(aRoot, aPath) {
     aRoot = ".";
   }
 
-  aRoot = aRoot.replace(/\/$/, '');
+  aRoot = aRoot.replace(/\/$/, "");
 
   // It is possible for the path to be above the root. In this case, simply
   // checking whether the root is a prefix of the path won't work. Instead, we
   // need to remove components from the root one by one, until either we find
   // a prefix that fits, or we run out of components to remove.
-  var level = 0;
-  while (aPath.indexOf(aRoot + '/') !== 0) {
-    var index = aRoot.lastIndexOf("/");
+  let level = 0;
+  while (aPath.indexOf(aRoot + "/") !== 0) {
+    const index = aRoot.lastIndexOf("/");
     if (index < 0) {
       return aPath;
     }
@@ -225,12 +281,12 @@ function relative(aRoot, aPath) {
 }
 exports.relative = relative;
 
-var supportsNullProto = (function () {
-  var obj = Object.create(null);
-  return !('__proto__' in obj);
+const supportsNullProto = (function() {
+  const obj = Object.create(null);
+  return !("__proto__" in obj);
 }());
 
-function identity (s) {
+function identity(s) {
   return s;
 }
 
@@ -245,7 +301,7 @@ function identity (s) {
  */
 function toSetString(aStr) {
   if (isProtoString(aStr)) {
-    return '$' + aStr;
+    return "$" + aStr;
   }
 
   return aStr;
@@ -266,12 +322,13 @@ function isProtoString(s) {
     return false;
   }
 
-  var length = s.length;
+  const length = s.length;
 
   if (length < 9 /* "__proto__".length */) {
     return false;
   }
 
+  /* eslint-disable no-multi-spaces */
   if (s.charCodeAt(length - 1) !== 95  /* '_' */ ||
       s.charCodeAt(length - 2) !== 95  /* '_' */ ||
       s.charCodeAt(length - 3) !== 111 /* 'o' */ ||
@@ -283,8 +340,9 @@ function isProtoString(s) {
       s.charCodeAt(length - 9) !== 95  /* '_' */) {
     return false;
   }
+  /* eslint-enable no-multi-spaces */
 
-  for (var i = length - 10; i >= 0; i--) {
+  for (let i = length - 10; i >= 0; i--) {
     if (s.charCodeAt(i) !== 36 /* '$' */) {
       return false;
     }
@@ -302,7 +360,7 @@ function isProtoString(s) {
  * stubbed out mapping.
  */
 function compareByOriginalPositions(mappingA, mappingB, onlyCompareOriginal) {
-  var cmp = strcmp(mappingA.source, mappingB.source);
+  let cmp = strcmp(mappingA.source, mappingB.source);
   if (cmp !== 0) {
     return cmp;
   }
@@ -341,7 +399,7 @@ exports.compareByOriginalPositions = compareByOriginalPositions;
  * mapping with a stubbed out mapping.
  */
 function compareByGeneratedPositionsDeflated(mappingA, mappingB, onlyCompareGenerated) {
-  var cmp = mappingA.generatedLine - mappingB.generatedLine;
+  let cmp = mappingA.generatedLine - mappingB.generatedLine;
   if (cmp !== 0) {
     return cmp;
   }
@@ -395,7 +453,7 @@ function strcmp(aStr1, aStr2) {
  * the generated positions are compared.
  */
 function compareByGeneratedPositionsInflated(mappingA, mappingB) {
-  var cmp = mappingA.generatedLine - mappingB.generatedLine;
+  let cmp = mappingA.generatedLine - mappingB.generatedLine;
   if (cmp !== 0) {
     return cmp;
   }
@@ -430,7 +488,7 @@ exports.compareByGeneratedPositionsInflated = compareByGeneratedPositionsInflate
  * JSON.
  */
 function parseSourceMapInput(str) {
-  return JSON.parse(str.replace(/^\)]}'[^\n]*\n/, ''));
+  return JSON.parse(str.replace(/^\)]}'[^\n]*\n/, ""));
 }
 exports.parseSourceMapInput = parseSourceMapInput;
 
@@ -439,12 +497,12 @@ exports.parseSourceMapInput = parseSourceMapInput;
  * URL, and the source map's URL.
  */
 function computeSourceURL(sourceRoot, sourceURL, sourceMapURL) {
-  sourceURL = sourceURL || '';
+  sourceURL = sourceURL || "";
 
   if (sourceRoot) {
     // This follows what Chrome does.
-    if (sourceRoot[sourceRoot.length - 1] !== '/' && sourceURL[0] !== '/') {
-      sourceRoot += '/';
+    if (sourceRoot[sourceRoot.length - 1] !== "/" && sourceURL[0] !== "/") {
+      sourceRoot += "/";
     }
     // The spec says:
     //   Line 4: An optional source root, useful for relocating source
@@ -469,13 +527,13 @@ function computeSourceURL(sourceRoot, sourceURL, sourceMapURL) {
   //   “sourceRoot”, the sources are resolved relative to the
   //   SourceMap (like resolving script src in a html document).
   if (sourceMapURL) {
-    var parsed = urlParse(sourceMapURL);
+    const parsed = urlParse(sourceMapURL);
     if (!parsed) {
       throw new Error("sourceMapURL could not be parsed");
     }
     if (parsed.path) {
       // Strip the last path component, but keep the "/".
-      var index = parsed.path.lastIndexOf('/');
+      const index = parsed.path.lastIndexOf("/");
       if (index >= 0) {
         parsed.path = parsed.path.substring(0, index + 1);
       }
diff --git a/node_modules/source-map/lib/wasm.js b/node_modules/source-map/lib/wasm.js
new file mode 100644
index 00000000..88b18bea
--- /dev/null
+++ b/node_modules/source-map/lib/wasm.js
@@ -0,0 +1,107 @@
+const readWasm = require("../lib/read-wasm");
+
+/**
+ * Provide the JIT with a nice shape / hidden class.
+ */
+function Mapping() {
+  this.generatedLine = 0;
+  this.generatedColumn = 0;
+  this.lastGeneratedColumn = null;
+  this.source = null;
+  this.originalLine = null;
+  this.originalColumn = null;
+  this.name = null;
+}
+
+let cachedWasm = null;
+
+module.exports = function wasm() {
+  if (cachedWasm) {
+    return cachedWasm;
+  }
+
+  const callbackStack = [];
+
+  cachedWasm = readWasm().then(buffer => {
+      return WebAssembly.instantiate(buffer, {
+        env: {
+          mapping_callback(
+            generatedLine,
+            generatedColumn,
+
+            hasLastGeneratedColumn,
+            lastGeneratedColumn,
+
+            hasOriginal,
+            source,
+            originalLine,
+            originalColumn,
+
+            hasName,
+            name
+          ) {
+            const mapping = new Mapping();
+            // JS uses 1-based line numbers, wasm uses 0-based.
+            mapping.generatedLine = generatedLine + 1;
+            mapping.generatedColumn = generatedColumn;
+
+            if (hasLastGeneratedColumn) {
+              // JS uses inclusive last generated column, wasm uses exclusive.
+              mapping.lastGeneratedColumn = lastGeneratedColumn - 1;
+            }
+
+            if (hasOriginal) {
+              mapping.source = source;
+              // JS uses 1-based line numbers, wasm uses 0-based.
+              mapping.originalLine = originalLine + 1;
+              mapping.originalColumn = originalColumn;
+
+              if (hasName) {
+                mapping.name = name;
+              }
+            }
+
+            callbackStack[callbackStack.length - 1](mapping);
+          },
+
+          start_all_generated_locations_for() { console.time("all_generated_locations_for"); },
+          end_all_generated_locations_for() { console.timeEnd("all_generated_locations_for"); },
+
+          start_compute_column_spans() { console.time("compute_column_spans"); },
+          end_compute_column_spans() { console.timeEnd("compute_column_spans"); },
+
+          start_generated_location_for() { console.time("generated_location_for"); },
+          end_generated_location_for() { console.timeEnd("generated_location_for"); },
+
+          start_original_location_for() { console.time("original_location_for"); },
+          end_original_location_for() { console.timeEnd("original_location_for"); },
+
+          start_parse_mappings() { console.time("parse_mappings"); },
+          end_parse_mappings() { console.timeEnd("parse_mappings"); },
+
+          start_sort_by_generated_location() { console.time("sort_by_generated_location"); },
+          end_sort_by_generated_location() { console.timeEnd("sort_by_generated_location"); },
+
+          start_sort_by_original_location() { console.time("sort_by_original_location"); },
+          end_sort_by_original_location() { console.timeEnd("sort_by_original_location"); },
+        }
+      });
+  }).then(Wasm => {
+    return {
+      exports: Wasm.instance.exports,
+      withMappingCallback: (mappingCallback, f) => {
+        callbackStack.push(mappingCallback);
+        try {
+          f();
+        } finally {
+          callbackStack.pop();
+        }
+      }
+    };
+  }).then(null, e => {
+    cachedWasm = null;
+    throw e;
+  });
+
+  return cachedWasm;
+};