removed autoprefix hover as it will have a high chance of making hover stopped working

1 files changed, 754 insertions, 909 deletions

diff --git a/node_modules/source-map/lib/source-map-consumer.js b/node_modules/source-map/lib/source-map-consumer.js
index 9aaf92f5..6abcc280 100644
--- a/node_modules/source-map/lib/source-map-consumer.js
+++ b/node_modules/source-map/lib/source-map-consumer.js
@@ -5,144 +5,248 @@
  * http://opensource.org/licenses/BSD-3-Clause
  */
 
-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 _factory(aSourceMap, aSourceMapURL);
+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) {
+  var sourceMap = aSourceMap;
+  if (typeof aSourceMap === 'string') {
+    sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
   }
 
-  static initialize(opts) {
-    readWasm.initialize(opts["lib/mappings.wasm"]);
-  }
+  return sourceMap.sections != null
+    ? new IndexedSourceMapConsumer(sourceMap)
+    : new BasicSourceMapConsumer(sourceMap);
+}
 
-  static fromSourceMap(aSourceMap, aSourceMapURL) {
-    return _factoryBSM(aSourceMap, aSourceMapURL);
-  }
+SourceMapConsumer.fromSourceMap = function(aSourceMap) {
+  return BasicSourceMapConsumer.fromSourceMap(aSourceMap);
+}
 
-  /**
-   * 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();
+/**
+ * The version of the source mapping spec that we are consuming.
+ */
+SourceMapConsumer.prototype._version = 3;
+
+// `__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', {
+  get: function () {
+    if (!this.__generatedMappings) {
+      this._parseMappings(this._mappings, this.sourceRoot);
     }
-  }
 
-  /**
-   * 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");
+    return this.__generatedMappings;
   }
+});
 
-  /**
-   * 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");
-  }
+SourceMapConsumer.prototype.__originalMappings = null;
+Object.defineProperty(SourceMapConsumer.prototype, '_originalMappings', {
+  get: function () {
+    if (!this.__originalMappings) {
+      this._parseMappings(this._mappings, this.sourceRoot);
+    }
 
-  /**
-   * 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");
+    return this.__originalMappings;
   }
+});
 
-  destroy() {
-    throw new Error("Subclasses must implement destroy");
-  }
-}
+SourceMapConsumer.prototype._charIsMappingSeparator =
+  function SourceMapConsumer_charIsMappingSeparator(aStr, index) {
+    var c = aStr.charAt(index);
+    return c === ";" || c === ",";
+  };
 
 /**
- * The version of the source mapping spec that we are consuming.
+ * 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).
  */
-SourceMapConsumer.prototype._version = 3;
+SourceMapConsumer.prototype._parseMappings =
+  function SourceMapConsumer_parseMappings(aStr, aSourceRoot) {
+    throw new Error("Subclasses must implement _parseMappings");
+  };
+
 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);
+      if (source != null && sourceRoot != null) {
+        source = util.join(sourceRoot, source);
+      }
+      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.
+ *   - column: Optional. the column number in the original source.
+ *
+ * and an array of objects is returned, each with the following properties:
+ *
+ *   - line: The line number in the generated source, or null.
+ *   - column: The column number in the generated source, or null.
+ */
+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)
+    };
+
+    if (this.sourceRoot != null) {
+      needle.source = util.relative(this.sourceRoot, needle.source);
+    }
+    if (!this._sources.has(needle.source)) {
+      return [];
+    }
+    needle.source = this._sources.indexOf(needle.source);
+
+    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;
 
 /**
@@ -150,13 +254,13 @@ exports.SourceMapConsumer = SourceMapConsumer;
  * query for information about the original file positions by giving it a file
  * position in the generated source.
  *
- * The first parameter is the raw source map (either as a JSON string, or
+ * The only parameter is the raw source map (either as a JSON string, or
  * already parsed to an object). According to the spec, source maps have the
  * following attributes:
  *
  *   - 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 referenced by individual mappings.
+ *   - names: An array of identifiers which can be referrenced 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.
@@ -173,348 +277,359 @@ exports.SourceMapConsumer = SourceMapConsumer;
  *       mappings: "AA,AB;;ABCDE;"
  *     }
  *
- * The second parameter, if given, is a string whose value is the URL
- * at which the source map was found.  This URL is used to compute the
- * sources array.
- *
  * [0]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit?pli=1#
  */
-class BasicSourceMapConsumer 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");
-      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);
-      }
-
-      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);
-      });
-
-      that.sourceRoot = sourceRoot;
-      that.sourcesContent = sourcesContent;
-      that._mappings = mappings;
-      that._sourceMapURL = aSourceMapURL;
-      that.file = file;
+function BasicSourceMapConsumer(aSourceMap) {
+  var sourceMap = aSourceMap;
+  if (typeof aSourceMap === 'string') {
+    sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
+  }
 
-      that._computedColumnSpans = false;
-      that._mappingsPtr = 0;
-      that._wasm = null;
+  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);
+  }
 
-      return wasm().then(w => {
-        that._wasm = w;
-        return that;
-      });
+  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;
     });
-  }
 
-  /**
-   * 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);
-    }
+  // 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.sourceRoot = sourceRoot;
+  this.sourcesContent = sourcesContent;
+  this._mappings = mappings;
+  this.file = file;
+}
 
-    if (this._sources.has(relativeSource)) {
-      return this._sources.indexOf(relativeSource);
-    }
+BasicSourceMapConsumer.prototype = Object.create(SourceMapConsumer.prototype);
+BasicSourceMapConsumer.prototype.consumer = SourceMapConsumer;
 
-    // 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.
+ * @returns BasicSourceMapConsumer
+ */
+BasicSourceMapConsumer.fromSourceMap =
+  function SourceMapConsumer_fromSourceMap(aSourceMap) {
+    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;
+
+    // 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.
+
+    var generatedMappings = aSourceMap._mappings.toArray().slice();
+    var destGeneratedMappings = smc.__generatedMappings = [];
+    var destOriginalMappings = smc.__originalMappings = [];
+
+    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;
+
+      if (srcMapping.source) {
+        destMapping.source = sources.indexOf(srcMapping.source);
+        destMapping.originalLine = srcMapping.originalLine;
+        destMapping.originalColumn = srcMapping.originalColumn;
+
+        if (srcMapping.name) {
+          destMapping.name = names.indexOf(srcMapping.name);
+        }
+
+        destOriginalMappings.push(destMapping);
       }
-    }
 
-    return -1;
-  }
+      destGeneratedMappings.push(destMapping);
+    }
 
-  /**
-   * 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());
-  }
+    quickSort(smc.__originalMappings, util.compareByOriginalPositions);
 
-  get sources() {
-    return this._absoluteSources.slice();
-  }
+    return smc;
+  };
 
-  _getMappingsPtr() {
-    if (this._mappingsPtr === 0) {
-      this._parseMappings(this._mappings, this.sourceRoot);
-    }
+/**
+ * The version of the source mapping spec that we are consuming.
+ */
+BasicSourceMapConsumer.prototype._version = 3;
 
-    return this._mappingsPtr;
+/**
+ * The list of original sources.
+ */
+Object.defineProperty(BasicSourceMapConsumer.prototype, 'sources', {
+  get: function () {
+    return this._sources.toArray().map(function (s) {
+      return this.sourceRoot != null ? util.join(this.sourceRoot, s) : s;
+    }, this);
   }
+});
 
-  /**
-   * 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);
-    }
+/**
+ * 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;
+}
 
-    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;
+/**
+ * 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);
+          }
 
-      throw new Error(msg);
-    }
-
-    this._mappingsPtr = mappingsPtr;
-  }
+          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');
+          }
 
-    this._wasm.withMappingCallback(
-      mapping => {
-        if (mapping.source !== null) {
-          mapping.source = this._sources.at(mapping.source);
-          mapping.source = util.computeSourceURL(sourceRoot, mapping.source, this._sourceMapURL);
+          cachedSegments[str] = segment;
+        }
 
-          if (mapping.name !== null) {
-            mapping.name = this._names.at(mapping.name);
+        // 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];
           }
         }
 
-        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.");
+        generatedMappings.push(mapping);
+        if (typeof mapping.originalLine === 'number') {
+          originalMappings.push(mapping);
         }
       }
-    );
-  }
+    }
 
-  allGeneratedPositionsFor(aArgs) {
-    let source = util.getArg(aArgs, "source");
-    const originalLine = util.getArg(aArgs, "line");
-    const originalColumn = aArgs.column || 0;
+    quickSort(generatedMappings, util.compareByGeneratedPositionsDeflated);
+    this.__generatedMappings = generatedMappings;
 
-    source = this._findSourceIndex(source);
-    if (source < 0) {
-      return [];
-    }
+    quickSort(originalMappings, util.compareByOriginalPositions);
+    this.__originalMappings = originalMappings;
+  };
 
-    if (originalLine < 1) {
-      throw new Error("Line numbers must be >= 1");
-    }
+/**
+ * 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.
 
-    if (originalColumn < 0) {
-      throw new Error("Column numbers must be >= 0");
+    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]);
     }
 
-    const mappings = [];
+    return binarySearch.search(aNeedle, aMappings, aComparator, aBias);
+  };
 
-    this._wasm.withMappingCallback(
-      m => {
-        let lastColumn = m.lastGeneratedColumn;
-        if (this._computedColumnSpans && lastColumn === null) {
-          lastColumn = Infinity;
+/**
+ * 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;
         }
-        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;
-  }
-
-  destroy() {
-    if (this._mappingsPtr !== 0) {
-      this._wasm.exports.free_mappings(this._mappingsPtr);
-      this._mappingsPtr = 0;
-    }
-  }
-
-  /**
-   * Compute the last column for each generated mapping. The last column is
-   * inclusive.
-   */
-  computeColumnSpans() {
-    if (this._computedColumnSpans) {
-      return;
+      // The last mapping for each line spans the entire line.
+      mapping.lastGeneratedColumn = Infinity;
     }
+  };
 
-    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")
+/**
+ * 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.
+ *   - column: The column number in the generated source.
+ *   - 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.
+ *   - column: The column number in the original source, or null.
+ *   - 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')
     };
 
-    if (needle.generatedLine < 1) {
-      throw new Error("Line numbers must be >= 1");
-    }
-
-    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;
-    }
+    var index = this._findMapping(
+      needle,
+      this._generatedMappings,
+      "generatedLine",
+      "generatedColumn",
+      util.compareByGeneratedPositionsDeflated,
+      util.getArg(aArgs, '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 (index >= 0) {
+      var mapping = this._generatedMappings[index];
 
-    if (mapping) {
       if (mapping.generatedLine === needle.generatedLine) {
-        let source = util.getArg(mapping, "source", null);
+        var source = util.getArg(mapping, 'source', null);
         if (source !== null) {
           source = this._sources.at(source);
-          source = util.computeSourceURL(this.sourceRoot, source, this._sourceMapURL);
+          if (this.sourceRoot != null) {
+            source = util.join(this.sourceRoot, source);
+          }
         }
-
-        let name = util.getArg(mapping, "name", null);
+        var name = util.getArg(mapping, 'name', null);
         if (name !== null) {
           name = this._names.at(name);
         }
-
         return {
-          source,
-          line: util.getArg(mapping, "originalLine", null),
-          column: util.getArg(mapping, "originalColumn", null),
-          name
+          source: source,
+          line: util.getArg(mapping, 'originalLine', null),
+          column: util.getArg(mapping, 'originalColumn', null),
+          name: name
         };
       }
     }
@@ -525,56 +640,56 @@ class BasicSourceMapConsumer extends SourceMapConsumer {
       column: null,
       name: null
     };
-  }
+  };
 
-  /**
-   * Return true if we have the source content for every source in the source
-   * map, false otherwise.
-   */
-  hasContentsOfAllSources() {
+/**
+ * Return true if we have the source content for every source in the source
+ * map, false otherwise.
+ */
+BasicSourceMapConsumer.prototype.hasContentsOfAllSources =
+  function BasicSourceMapConsumer_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.
-   */
-  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.
+ */
+BasicSourceMapConsumer.prototype.sourceContentFor =
+  function SourceMapConsumer_sourceContentFor(aSource, nullOnMissing) {
     if (!this.sourcesContent) {
       return null;
     }
 
-    const index = this._findSourceIndex(aSource);
-    if (index >= 0) {
-      return this.sourcesContent[index];
+    if (this.sourceRoot != null) {
+      aSource = util.relative(this.sourceRoot, aSource);
     }
 
-    let relativeSource = aSource;
-    if (this.sourceRoot != null) {
-      relativeSource = util.relative(this.sourceRoot, relativeSource);
+    if (this._sources.has(aSource)) {
+      return this.sourcesContent[this._sources.indexOf(aSource)];
     }
 
-    let url;
+    var 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.
-      const fileUriAbsPath = relativeSource.replace(/^file:\/\//, "");
+      var fileUriAbsPath = aSource.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 == "/")
-          && this._sources.has("/" + relativeSource)) {
-        return this.sourcesContent[this._sources.indexOf("/" + relativeSource)];
+          && this._sources.has("/" + aSource)) {
+        return this.sourcesContent[this._sources.indexOf("/" + aSource)];
       }
     }
 
@@ -585,84 +700,68 @@ class BasicSourceMapConsumer extends SourceMapConsumer {
     if (nullOnMissing) {
       return null;
     }
+    else {
+      throw new Error('"' + aSource + '" is not in the SourceMap.');
+    }
+  };
 
-    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) {
+/**
+ * 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.
+ *   - column: The column number in the original source.
+ *   - 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.
+ *   - column: The column number in the generated source, or null.
+ */
+BasicSourceMapConsumer.prototype.generatedPositionFor =
+  function SourceMapConsumer_generatedPositionFor(aArgs) {
+    var source = util.getArg(aArgs, 'source');
+    if (this.sourceRoot != null) {
+      source = util.relative(this.sourceRoot, source);
+    }
+    if (!this._sources.has(source)) {
       return {
         line: null,
         column: null,
         lastColumn: null
       };
     }
+    source = this._sources.indexOf(source);
 
-    const needle = {
-      source,
-      originalLine: util.getArg(aArgs, "line"),
-      originalColumn: util.getArg(aArgs, "column")
+    var needle = {
+      source: source,
+      originalLine: util.getArg(aArgs, 'line'),
+      originalColumn: util.getArg(aArgs, 'column')
     };
 
-    if (needle.originalLine < 1) {
-      throw new Error("Line numbers must be >= 1");
-    }
-
-    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;
-    }
+    var index = this._findMapping(
+      needle,
+      this._originalMappings,
+      "originalLine",
+      "originalColumn",
+      util.compareByOriginalPositions,
+      util.getArg(aArgs, '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 (index >= 0) {
+      var mapping = this._originalMappings[index];
 
-    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,
+          line: util.getArg(mapping, 'generatedLine', null),
+          column: util.getArg(mapping, 'generatedColumn', null),
+          lastColumn: util.getArg(mapping, 'lastGeneratedColumn', null)
         };
       }
     }
@@ -672,10 +771,8 @@ class BasicSourceMapConsumer extends SourceMapConsumer {
       column: null,
       lastColumn: null
     };
-  }
-}
+  };
 
-BasicSourceMapConsumer.prototype.consumer = SourceMapConsumer;
 exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
 
 /**
@@ -684,7 +781,7 @@ exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
  * that it takes "indexed" source maps (i.e. ones with a "sections" field) as
  * input.
  *
- * The first parameter is a raw source map (either as a JSON string, or already
+ * The only parameter is a raw source map (either as a JSON string, or already
  * parsed to an object). According to the spec for indexed source maps, they
  * have the following attributes:
  *
@@ -721,197 +818,114 @@ exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
  *    }],
  *  }
  *
- * The second parameter, if given, is a string whose value is the URL
- * at which the source map was found.  This URL is used to compute the
- * sources array.
- *
  * [0]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k/edit#heading=h.535es3xeprgt
  */
-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;
-      });
-    });
+function IndexedSourceMapConsumer(aSourceMap) {
+  var sourceMap = aSourceMap;
+  if (typeof aSourceMap === 'string') {
+    sourceMap = JSON.parse(aSourceMap.replace(/^\)\]\}'/, ''));
   }
 
-  // `__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();
-    }
+  var version = util.getArg(sourceMap, 'version');
+  var sections = util.getArg(sourceMap, 'sections');
 
-    return this.__generatedMappings;
+  if (version != this._version) {
+    throw new Error('Unsupported version: ' + version);
   }
 
-  get _originalMappings() {
-    if (!this.__originalMappings) {
-      this._sortOriginalMappings();
+  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.');
     }
+    var offset = util.getArg(s, 'offset');
+    var offsetLine = util.getArg(offset, 'line');
+    var offsetColumn = util.getArg(offset, 'column');
 
-    return this.__originalMappings;
-  }
-
-  get _generatedMappingsUnsorted() {
-    if (!this.__generatedMappingsUnsorted) {
-      this._parseMappings(this._mappings, this.sourceRoot);
+    if (offsetLine < lastOffset.line ||
+        (offsetLine === lastOffset.line && offsetColumn < lastOffset.column)) {
+      throw new Error('Section offsets must be ordered and non-overlapping.');
     }
+    lastOffset = offset;
 
-    return this.__generatedMappingsUnsorted;
-  }
-
-  get _originalMappingsUnsorted() {
-    if (!this.__originalMappingsUnsorted) {
-      this._parseMappings(this._mappings, this.sourceRoot);
+    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'))
     }
+  });
+}
 
-    return this.__originalMappingsUnsorted;
-  }
-
-  _sortGeneratedMappings() {
-    const mappings = this._generatedMappingsUnsorted;
-    mappings.sort(util.compareByGeneratedPositionsDeflated);
-    this.__generatedMappings = mappings;
-  }
+IndexedSourceMapConsumer.prototype = Object.create(SourceMapConsumer.prototype);
+IndexedSourceMapConsumer.prototype.constructor = SourceMapConsumer;
 
-  _sortOriginalMappings() {
-    const mappings = this._originalMappingsUnsorted;
-    mappings.sort(util.compareByOriginalPositions);
-    this.__originalMappings = mappings;
-  }
+/**
+ * The version of the source mapping spec that we are consuming.
+ */
+IndexedSourceMapConsumer.prototype._version = 3;
 
-  /**
-   * 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++) {
+/**
+ * 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++) {
         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.
-   */
-  originalPositionFor(aArgs) {
-    const 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.
+ *   - column: The column number in the generated source.
+ *
+ * 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.
+ *   - column: The column number in the original source, or null.
+ *   - 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')
     };
 
     // Find the section containing the generated position we're trying to map
     // to an original position.
-    const sectionIndex = binarySearch.search(needle, this._sections,
-      function(aNeedle, section) {
-        const cmp = aNeedle.generatedLine - section.generatedOffset.generatedLine;
+    var sectionIndex = binarySearch.search(needle, this._sections,
+      function(needle, section) {
+        var cmp = needle.generatedLine - section.generatedOffset.generatedLine;
         if (cmp) {
           return cmp;
         }
 
-        return (aNeedle.generatedColumn -
+        return (needle.generatedColumn -
                 section.generatedOffset.generatedColumn);
       });
-    const section = this._sections[sectionIndex];
+    var section = this._sections[sectionIndex];
 
     if (!section) {
       return {
@@ -931,28 +945,30 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
          : 0),
       bias: aArgs.bias
     });
-  }
+  };
 
-  /**
-   * 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 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 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.
-   */
-  sourceContentFor(aSource, nullOnMissing) {
-    for (let i = 0; i < this._sections.length; i++) {
-      const 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.
+ */
+IndexedSourceMapConsumer.prototype.sourceContentFor =
+  function IndexedSourceMapConsumer_sourceContentFor(aSource, nullOnMissing) {
+    for (var i = 0; i < this._sections.length; i++) {
+      var section = this._sections[i];
 
-      const content = section.consumer.sourceContentFor(aSource, true);
+      var content = section.consumer.sourceContentFor(aSource, true);
       if (content) {
         return content;
       }
@@ -960,39 +976,38 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
     if (nullOnMissing) {
       return null;
     }
-    throw new Error('"' + aSource + '" is not in the SourceMap.');
-  }
+    else {
+      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.
-   */
-  generatedPositionFor(aArgs) {
-    for (let i = 0; i < this._sections.length; i++) {
-      const 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.
+ *   - column: The column number in the original source.
+ *
+ * and an object is returned with the following properties:
+ *
+ *   - line: The line number in the generated source, or null.
+ *   - column: The column number in the generated source, or null.
+ */
+IndexedSourceMapConsumer.prototype.generatedPositionFor =
+  function IndexedSourceMapConsumer_generatedPositionFor(aArgs) {
+    for (var i = 0; i < this._sections.length; i++) {
+      var 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.sources.indexOf(util.getArg(aArgs, 'source')) === -1) {
         continue;
       }
-      const generatedPosition = section.consumer.generatedPositionFor(aArgs);
+      var generatedPosition = section.consumer.generatedPositionFor(aArgs);
       if (generatedPosition) {
-        const ret = {
+        var ret = {
           line: generatedPosition.line +
             (section.generatedOffset.generatedLine - 1),
           column: generatedPosition.column +
@@ -1008,45 +1023,40 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
       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).
-   */
-  _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);
+/**
+ * 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);
+        if (section.consumer.sourceRoot !== null) {
+          source = util.join(section.consumer.sourceRoot, source);
+        }
         this._sources.add(source);
         source = this._sources.indexOf(source);
 
-        let name = null;
-        if (mapping.name) {
-          this._names.add(mapping.name);
-          name = this._names.indexOf(mapping.name);
-        }
+        var name = section.consumer._names.at(mapping.name);
+        this._names.add(name);
+        name = this._names.indexOf(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.
-        const adjustedMapping = {
-          source,
+        var adjustedMapping = {
+          source: source,
           generatedLine: mapping.generatedLine +
             (section.generatedOffset.generatedLine - 1),
           generatedColumn: mapping.generatedColumn +
@@ -1055,183 +1065,18 @@ class IndexedSourceMapConsumer extends SourceMapConsumer {
             : 0),
           originalLine: mapping.originalLine,
           originalColumn: mapping.originalColumn,
-          name
+          name: name
         };
 
-        generatedMappings.push(adjustedMapping);
-        if (typeof adjustedMapping.originalLine === "number") {
-          originalMappings.push(adjustedMapping);
+        this.__generatedMappings.push(adjustedMapping);
+        if (typeof adjustedMapping.originalLine === 'number') {
+          this.__originalMappings.push(adjustedMapping);
         }
       }
     }
-  }
 
-  eachMapping(aCallback, aContext, aOrder) {
-    const context = aContext || null;
-    const order = aOrder || SourceMapConsumer.GENERATED_ORDER;
+    quickSort(this.__generatedMappings, util.compareByGeneratedPositionsDeflated);
+    quickSort(this.__originalMappings, util.compareByOriginalPositions);
+  };
 
-    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);
-}