Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

14 files changed, 3026 insertions, 0 deletions

diff --git a/devtools/client/shared/vendor/source-map/lib/array-set.js b/devtools/client/shared/vendor/source-map/lib/array-set.js
new file mode 100644
index 0000000000..d2ed9cd135
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/array-set.js
@@ -0,0 +1,100 @@
+/* -*- 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
+ */
+
+/**
+ * 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.
+ */
+class ArraySet {
+  constructor() {
+    this._array = [];
+    this._set = new Map();
+  }
+
+  /**
+   * 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;
+  }
+
+  /**
+   * 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;
+  }
+
+  /**
+   * 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);
+    }
+  }
+
+  /**
+   * 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
+   */
+  indexOf(aStr) {
+    const idx = this._set.get(aStr);
+    if (idx >= 0) {
+      return idx;
+    }
+    throw new Error('"' + aStr + '" is not in the set.');
+  }
+
+  /**
+   * 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);
+  }
+
+  /**
+   * 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/devtools/client/shared/vendor/source-map/lib/base64-vlq.js b/devtools/client/shared/vendor/source-map/lib/base64-vlq.js
new file mode 100644
index 0000000000..2daed1eb5a
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/base64-vlq.js
@@ -0,0 +1,94 @@
+/* -*- 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
+ *
+ * Based on the Base 64 VLQ implementation in Closure Compiler:
+ * https://code.google.com/p/closure-compiler/source/browse/trunk/src/com/google/debugging/sourcemap/Base64VLQ.java
+ *
+ * Copyright 2011 The Closure Compiler Authors. All rights reserved.
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials provided
+ *    with the distribution.
+ *  * Neither the name of Google Inc. nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+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,
+// the next four bits are the actual value, and the 6th bit is the
+// continuation bit. The continuation bit tells us whether there are more
+// digits in this value following this digit.
+//
+//   Continuation
+//   |    Sign
+//   |    |
+//   V    V
+//   101011
+
+const VLQ_BASE_SHIFT = 5;
+
+// binary: 100000
+const VLQ_BASE = 1 << VLQ_BASE_SHIFT;
+
+// binary: 011111
+const VLQ_BASE_MASK = VLQ_BASE - 1;
+
+// binary: 100000
+const VLQ_CONTINUATION_BIT = VLQ_BASE;
+
+/**
+ * Converts from a two-complement value to a value where the sign bit is
+ * placed in the least significant bit.  For example, as decimals:
+ *   1 becomes 2 (10 binary), -1 becomes 3 (11 binary)
+ *   2 becomes 4 (100 binary), -2 becomes 5 (101 binary)
+ */
+function toVLQSigned(aValue) {
+  return aValue < 0 ? (-aValue << 1) + 1 : (aValue << 1) + 0;
+}
+
+/**
+ * Returns the base 64 VLQ encoded value.
+ */
+exports.encode = function base64VLQ_encode(aValue) {
+  let encoded = "";
+  let digit;
+
+  let vlq = toVLQSigned(aValue);
+
+  do {
+    digit = vlq & VLQ_BASE_MASK;
+    vlq >>>= VLQ_BASE_SHIFT;
+    if (vlq > 0) {
+      // There are still more digits in this value, so we must make sure the
+      // continuation bit is marked.
+      digit |= VLQ_CONTINUATION_BIT;
+    }
+    encoded += base64.encode(digit);
+  } while (vlq > 0);
+
+  return encoded;
+};
diff --git a/devtools/client/shared/vendor/source-map/lib/base64.js b/devtools/client/shared/vendor/source-map/lib/base64.js
new file mode 100644
index 0000000000..939abc8e1e
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/base64.js
@@ -0,0 +1,19 @@
+/* -*- 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
+ */
+
+const intToCharMap =
+  "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".split("");
+
+/**
+ * Encode an integer in the range of 0 to 63 to a single base 64 digit.
+ */
+exports.encode = function (number) {
+  if (0 <= number && number < intToCharMap.length) {
+    return intToCharMap[number];
+  }
+  throw new TypeError("Must be between 0 and 63: " + number);
+};
diff --git a/devtools/client/shared/vendor/source-map/lib/binary-search.js b/devtools/client/shared/vendor/source-map/lib/binary-search.js
new file mode 100644
index 0000000000..db65ccd12e
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/binary-search.js
@@ -0,0 +1,113 @@
+/* -*- 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
+ */
+
+exports.GREATEST_LOWER_BOUND = 1;
+exports.LEAST_UPPER_BOUND = 2;
+
+/**
+ * Recursive implementation of binary search.
+ *
+ * @param aLow Indices here and lower do not contain the needle.
+ * @param aHigh Indices here and higher do not contain the needle.
+ * @param aNeedle The element being searched for.
+ * @param aHaystack The non-empty array being searched.
+ * @param aCompare Function which takes two elements and returns -1, 0, or 1.
+ * @param aBias Either 'binarySearch.GREATEST_LOWER_BOUND' or
+ *     'binarySearch.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.
+ */
+function recursiveSearch(aLow, aHigh, aNeedle, aHaystack, aCompare, aBias) {
+  // This function terminates when one of the following is true:
+  //
+  //   1. We find the exact element we are looking for.
+  //
+  //   2. We did not find the exact element, but we can return the index of
+  //      the next-closest element.
+  //
+  //   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.
+  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) {
+    // Our needle is greater than aHaystack[mid].
+    if (aHigh - mid > 1) {
+      // The element is in the upper half.
+      return recursiveSearch(mid, aHigh, aNeedle, aHaystack, aCompare, aBias);
+    }
+
+    // The exact needle element was not found in this haystack. Determine if
+    // 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;
+    }
+    return mid;
+  }
+
+  // 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;
+}
+
+/**
+ * This is an implementation of binary search which will always try and return
+ * the index of the closest element if there is no exact hit. This is because
+ * mappings between original and generated line/col pairs are single points,
+ * and there is an implicit region between each of them, so a miss just means
+ * that you aren't on the very start of a region.
+ *
+ * @param aNeedle The element you are looking for.
+ * @param aHaystack The array that is being searched.
+ * @param aCompare A function which takes the needle and an element in the
+ *     array and returns -1, 0, or 1 depending on whether the needle is less
+ *     than, equal to, or greater than the element, respectively.
+ * @param aBias Either 'binarySearch.GREATEST_LOWER_BOUND' or
+ *     'binarySearch.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 'binarySearch.GREATEST_LOWER_BOUND'.
+ */
+exports.search = function search(aNeedle, aHaystack, aCompare, aBias) {
+  if (aHaystack.length === 0) {
+    return -1;
+  }
+
+  let index = recursiveSearch(
+    -1,
+    aHaystack.length,
+    aNeedle,
+    aHaystack,
+    aCompare,
+    aBias || exports.GREATEST_LOWER_BOUND
+  );
+  if (index < 0) {
+    return -1;
+  }
+
+  // We have found either the exact element, or the next-closest element to
+  // the one we are searching for. However, there may be more than one such
+  // element. Make sure we always return the smallest of these.
+  while (index - 1 >= 0) {
+    if (aCompare(aHaystack[index], aHaystack[index - 1], true) !== 0) {
+      break;
+    }
+    --index;
+  }
+
+  return index;
+};
diff --git a/devtools/client/shared/vendor/source-map/lib/mapping-list.js b/devtools/client/shared/vendor/source-map/lib/mapping-list.js
new file mode 100644
index 0000000000..ece3c2ccc1
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/mapping-list.js
@@ -0,0 +1,83 @@
+/* -*- Mode: js; js-indent-level: 2; -*- */
+/*
+ * Copyright 2014 Mozilla Foundation and contributors
+ * Licensed under the New BSD license. See LICENSE or:
+ * http://opensource.org/licenses/BSD-3-Clause
+ */
+
+const util = require("./util");
+
+/**
+ * Determine whether mappingB is after mappingA with respect to generated
+ * position.
+ */
+function generatedPositionAfter(mappingA, mappingB) {
+  // Optimized for most common case
+  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 negligible overhead in general
+ * case for a large speedup in case of mappings being added in order.
+ */
+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.
+   */
+  unsortedForEach(aCallback, aThisArg) {
+    this._array.forEach(aCallback, aThisArg);
+  }
+
+  /**
+   * 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.
+   */
+  toArray() {
+    if (!this._sorted) {
+      this._array.sort(util.compareByGeneratedPositionsInflated);
+      this._sorted = true;
+    }
+    return this._array;
+  }
+}
+
+exports.MappingList = MappingList;
diff --git a/devtools/client/shared/vendor/source-map/lib/mappings.wasm b/devtools/client/shared/vendor/source-map/lib/mappings.wasm
new file mode 100644
index 0000000000..cdcc2958c0
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/mappings.wasm
diff --git a/devtools/client/shared/vendor/source-map/lib/moz.build b/devtools/client/shared/vendor/source-map/lib/moz.build
new file mode 100644
index 0000000000..ccd2457b17
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/moz.build
@@ -0,0 +1,21 @@
+# -*- Mode: python; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+DevToolsModules(
+    "array-set.js",
+    "base64-vlq.js",
+    "base64.js",
+    "binary-search.js",
+    "mapping-list.js",
+    "mappings.wasm",
+    "read-wasm.js",
+    "source-map-consumer.js",
+    "source-map-generator.js",
+    "source-node.js",
+    "url.js",
+    "util.js",
+    "wasm.js",
+)
diff --git a/devtools/client/shared/vendor/source-map/lib/read-wasm.js b/devtools/client/shared/vendor/source-map/lib/read-wasm.js
new file mode 100644
index 0000000000..75d7bd5415
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/read-wasm.js
@@ -0,0 +1,46 @@
+"use strict";
+
+const isNode =
+  typeof process !== "undefined" &&
+  process.versions != null &&
+  process.versions.node != null;
+
+let mappingsWasm = null;
+
+if (isNode) {
+  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);
+      });
+    });
+  };
+} else {
+  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;
+};
diff --git a/devtools/client/shared/vendor/source-map/lib/source-map-consumer.js b/devtools/client/shared/vendor/source-map/lib/source-map-consumer.js
new file mode 100644
index 0000000000..be1289d990
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/source-map-consumer.js
@@ -0,0 +1,1078 @@
+/* -*- 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
+ */
+
+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);
+  }
+
+  static initialize(opts) {
+    readWasm.initialize(opts["lib/mappings.wasm"]);
+  }
+
+  static fromSourceMap(aSourceMap, aSourceMapURL) {
+    return _factoryBSM(aSourceMap, aSourceMapURL);
+  }
+
+  /**
+   * 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();
+    }
+  }
+
+  /**
+   * 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");
+  }
+
+  /**
+   * 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");
+  }
+
+  destroy() {
+    throw new Error("Subclasses must implement destroy");
+  }
+}
+
+/**
+ * The version of the source mapping spec that we are consuming.
+ */
+SourceMapConsumer.prototype._version = 3;
+SourceMapConsumer.GENERATED_ORDER = 1;
+SourceMapConsumer.ORIGINAL_ORDER = 2;
+
+SourceMapConsumer.GREATEST_LOWER_BOUND = 1;
+SourceMapConsumer.LEAST_UPPER_BOUND = 2;
+
+exports.SourceMapConsumer = SourceMapConsumer;
+
+/**
+ * A BasicSourceMapConsumer instance represents a parsed source map which we can
+ * 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
+ * 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.
+ *   - 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.
+ *   - file: Optional. The generated file this source map is associated with.
+ *
+ * Here is an example source map, taken from the source map spec[0]:
+ *
+ *     {
+ *       version : 3,
+ *       file: "out.js",
+ *       sourceRoot : "",
+ *       sources: ["foo.js", "bar.js"],
+ *       names: ["src", "maps", "are", "fun"],
+ *       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");
+      const sources = util.getArg(sourceMap, "sources").map(String);
+      // 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", []);
+      const 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);
+      const x_google_ignoreList = util.getArg(
+        sourceMap,
+        "x_google_ignoreList",
+        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);
+      }
+
+      that._sourceLookupCache = new Map();
+
+      // 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 = ArraySet.fromArray(
+        that._sources.toArray().map(function (s) {
+          return util.computeSourceURL(sourceRoot, s, aSourceMapURL);
+        }),
+        true
+      );
+
+      that.sourceRoot = sourceRoot;
+      that.sourcesContent = sourcesContent;
+      that._mappings = mappings;
+      that._sourceMapURL = aSourceMapURL;
+      that.file = file;
+      that.x_google_ignoreList = x_google_ignoreList;
+
+      that._computedColumnSpans = false;
+      that._mappingsPtr = 0;
+      that._wasm = null;
+
+      return wasm().then(w => {
+        that._wasm = w;
+        return that;
+      });
+    });
+  }
+
+  /**
+   * Utility function to find the index of a source.  Returns -1 if not
+   * found.
+   */
+  _findSourceIndex(aSource) {
+    // In the most common usecases, we'll be constantly looking up the index for the same source
+    // files, so we cache the index lookup to avoid constantly recomputing the full URLs.
+    const cachedIndex = this._sourceLookupCache.get(aSource);
+    if (typeof cachedIndex === "number") {
+      return cachedIndex;
+    }
+
+    // Treat the source as map-relative overall by default.
+    const sourceAsMapRelative = util.computeSourceURL(
+      null,
+      aSource,
+      this._sourceMapURL
+    );
+    if (this._absoluteSources.has(sourceAsMapRelative)) {
+      const index = this._absoluteSources.indexOf(sourceAsMapRelative);
+      this._sourceLookupCache.set(aSource, index);
+      return index;
+    }
+
+    // Fall back to treating the source as sourceRoot-relative.
+    const sourceAsSourceRootRelative = util.computeSourceURL(
+      this.sourceRoot,
+      aSource,
+      this._sourceMapURL
+    );
+    if (this._absoluteSources.has(sourceAsSourceRootRelative)) {
+      const index = this._absoluteSources.indexOf(sourceAsSourceRootRelative);
+      this._sourceLookupCache.set(aSource, index);
+      return index;
+    }
+
+    // To avoid this cache growing forever, we do not cache lookup misses.
+    return -1;
+  }
+
+  /**
+   * 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());
+  }
+
+  get sources() {
+    return this._absoluteSources.toArray();
+  }
+
+  _getMappingsPtr() {
+    if (this._mappingsPtr === 0) {
+      this._parseMappings();
+    }
+
+    return this._mappingsPtr;
+  }
+
+  /**
+   * 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() {
+    const aStr = this._mappings;
+    const size = aStr.length;
+
+    // Interpret signed result of allocate_mappings as unsigned, otherwise
+    // addresses higher than 2GB will be negative.
+    const mappingsBufPtr = this._wasm.exports.allocate_mappings(size) >>> 0;
+    const mappingsBuf = new Uint8Array(
+      this._wasm.exports.memory.buffer,
+      mappingsBufPtr,
+      size
+    );
+    for (let i = 0; i < size; i++) {
+      mappingsBuf[i] = aStr.charCodeAt(i);
+    }
+
+    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 `wasm-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;
+      }
+
+      throw new Error(msg);
+    }
+
+    this._mappingsPtr = mappingsPtr;
+  }
+
+  eachMapping(aCallback, aContext, aOrder) {
+    const context = aContext || null;
+    const order = aOrder || SourceMapConsumer.GENERATED_ORDER;
+
+    this._wasm.withMappingCallback(
+      mapping => {
+        if (mapping.source !== null) {
+          mapping.source = this._absoluteSources.at(mapping.source);
+
+          if (mapping.name !== null) {
+            mapping.name = this._names.at(mapping.name);
+          }
+        }
+        if (this._computedColumnSpans && mapping.lastGeneratedColumn === null) {
+          mapping.lastGeneratedColumn = Infinity;
+        }
+
+        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.");
+        }
+      }
+    );
+  }
+
+  allGeneratedPositionsFor(aArgs) {
+    let source = util.getArg(aArgs, "source");
+    const originalLine = util.getArg(aArgs, "line");
+    const originalColumn = aArgs.column || 0;
+
+    source = this._findSourceIndex(source);
+    if (source < 0) {
+      return [];
+    }
+
+    if (originalLine < 1) {
+      throw new Error("Line numbers must be >= 1");
+    }
+
+    if (originalColumn < 0) {
+      throw new Error("Column numbers must be >= 0");
+    }
+
+    const mappings = [];
+
+    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;
+  }
+
+  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;
+    }
+
+    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"),
+    };
+
+    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;
+    }
+
+    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) {
+        let source = util.getArg(mapping, "source", null);
+        if (source !== null) {
+          source = this._absoluteSources.at(source);
+        }
+
+        let 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,
+        };
+      }
+    }
+
+    return {
+      source: null,
+      line: null,
+      column: null,
+      name: null,
+    };
+  }
+
+  /**
+   * 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;
+      })
+    );
+  }
+
+  /**
+   * 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;
+    }
+
+    const index = this._findSourceIndex(aSource);
+    if (index >= 0) {
+      return this.sourcesContent[index];
+    }
+
+    // This function is used recursively from
+    // IndexedSourceMapConsumer.prototype.sourceContentFor. In that case, we
+    // don't want to throw if we can't find the source - we just want to
+    // return null, so we provide a flag to exit gracefully.
+    if (nullOnMissing) {
+      return null;
+    }
+
+    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.
+   *   - 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 {
+        line: null,
+        column: null,
+        lastColumn: null,
+      };
+    }
+
+    const needle = {
+      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;
+    }
+
+    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,
+        };
+      }
+    }
+
+    return {
+      line: null,
+      column: null,
+      lastColumn: null,
+    };
+  }
+}
+
+BasicSourceMapConsumer.prototype.consumer = SourceMapConsumer;
+exports.BasicSourceMapConsumer = BasicSourceMapConsumer;
+
+/**
+ * An IndexedSourceMapConsumer instance represents a parsed source map which
+ * we can query for information. It differs from BasicSourceMapConsumer in
+ * 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
+ * parsed to an object). According to the spec for indexed source maps, they
+ * have the following attributes:
+ *
+ *   - version: Which version of the source map spec this map is following.
+ *   - file: Optional. The generated file this source map is associated with.
+ *   - sections: A list of section definitions.
+ *
+ * Each value under the "sections" field has two fields:
+ *   - offset: The offset into the original specified at which this section
+ *       begins to apply, defined as an object with a "line" and "column"
+ *       field.
+ *   - map: A source map definition. This source map could also be indexed,
+ *       but doesn't have to be.
+ *
+ * Instead of the "map" field, it's also possible to have a "url" field
+ * specifying a URL to retrieve a source map from, but that's currently
+ * unsupported.
+ *
+ * Here's an example source map, taken from the source map spec[0], but
+ * modified to omit a section which uses the "url" field.
+ *
+ *  {
+ *    version : 3,
+ *    file: "app.js",
+ *    sections: [{
+ *      offset: {line:100, column:10},
+ *      map: {
+ *        version : 3,
+ *        file: "section.js",
+ *        sources: ["foo.js", "bar.js"],
+ *        names: ["src", "maps", "are", "fun"],
+ *        mappings: "AAAA,E;;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#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);
+      }
+
+      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;
+      });
+    });
+  }
+
+  /**
+   * 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.
+   */
+  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.
+    const sectionIndex = binarySearch.search(
+      needle,
+      this._sections,
+      function (aNeedle, section) {
+        const cmp =
+          aNeedle.generatedLine - section.generatedOffset.generatedLine;
+        if (cmp) {
+          return cmp;
+        }
+
+        return (
+          aNeedle.generatedColumn - section.generatedOffset.generatedColumn
+        );
+      }
+    );
+    const section = this._sections[sectionIndex];
+
+    if (!section) {
+      return {
+        source: null,
+        line: null,
+        column: null,
+        name: null,
+      };
+    }
+
+    return section.consumer.originalPositionFor({
+      line: needle.generatedLine - (section.generatedOffset.generatedLine - 1),
+      column:
+        needle.generatedColumn -
+        (section.generatedOffset.generatedLine === needle.generatedLine
+          ? section.generatedOffset.generatedColumn - 1
+          : 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 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];
+
+      const content = section.consumer.sourceContentFor(aSource, true);
+      if (content) {
+        return content;
+      }
+    }
+    if (nullOnMissing) {
+      return null;
+    }
+    throw new Error('"' + aSource + '" is not in the SourceMap.');
+  }
+
+  _findSectionIndex(source) {
+    for (let i = 0; i < this._sections.length; i++) {
+      const { consumer } = this._sections[i];
+      if (consumer._findSourceIndex(source) !== -1) {
+        return i;
+      }
+    }
+    return -1;
+  }
+
+  /**
+   * 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) {
+    const index = this._findSectionIndex(util.getArg(aArgs, "source"));
+    const section = index >= 0 ? this._sections[index] : null;
+    const nextSection =
+      index >= 0 && index + 1 < this._sections.length
+        ? this._sections[index + 1]
+        : null;
+
+    const generatedPosition =
+      section && section.consumer.generatedPositionFor(aArgs);
+    if (generatedPosition && generatedPosition.line !== null) {
+      const lineShift = section.generatedOffset.generatedLine - 1;
+      const columnShift = section.generatedOffset.generatedColumn - 1;
+
+      if (generatedPosition.line === 1) {
+        generatedPosition.column += columnShift;
+        if (typeof generatedPosition.lastColumn === "number") {
+          generatedPosition.lastColumn += columnShift;
+        }
+      }
+
+      if (
+        generatedPosition.lastColumn === Infinity &&
+        nextSection &&
+        generatedPosition.line === nextSection.generatedOffset.generatedLine
+      ) {
+        generatedPosition.lastColumn =
+          nextSection.generatedOffset.generatedColumn - 2;
+      }
+      generatedPosition.line += lineShift;
+
+      return generatedPosition;
+    }
+
+    return {
+      line: null,
+      column: null,
+      lastColumn: null,
+    };
+  }
+
+  allGeneratedPositionsFor(aArgs) {
+    const index = this._findSectionIndex(util.getArg(aArgs, "source"));
+    const section = index >= 0 ? this._sections[index] : null;
+    const nextSection =
+      index >= 0 && index + 1 < this._sections.length
+        ? this._sections[index + 1]
+        : null;
+
+    if (!section) return [];
+
+    return section.consumer
+      .allGeneratedPositionsFor(aArgs)
+      .map(generatedPosition => {
+        const lineShift = section.generatedOffset.generatedLine - 1;
+        const columnShift = section.generatedOffset.generatedColumn - 1;
+
+        if (generatedPosition.line === 1) {
+          generatedPosition.column += columnShift;
+          if (typeof generatedPosition.lastColumn === "number") {
+            generatedPosition.lastColumn += columnShift;
+          }
+        }
+
+        if (
+          generatedPosition.lastColumn === Infinity &&
+          nextSection &&
+          generatedPosition.line === nextSection.generatedOffset.generatedLine
+        ) {
+          generatedPosition.lastColumn =
+            nextSection.generatedOffset.generatedColumn - 2;
+        }
+        generatedPosition.line += lineShift;
+
+        return generatedPosition;
+      });
+  }
+
+  eachMapping(aCallback, aContext, aOrder) {
+    this._sections.forEach((section, index) => {
+      const nextSection =
+        index + 1 < this._sections.length ? this._sections[index + 1] : null;
+      const { generatedOffset } = section;
+
+      const lineShift = generatedOffset.generatedLine - 1;
+      const columnShift = generatedOffset.generatedColumn - 1;
+
+      section.consumer.eachMapping(
+        function (mapping) {
+          if (mapping.generatedLine === 1) {
+            mapping.generatedColumn += columnShift;
+
+            if (typeof mapping.lastGeneratedColumn === "number") {
+              mapping.lastGeneratedColumn += columnShift;
+            }
+          }
+
+          if (
+            mapping.lastGeneratedColumn === Infinity &&
+            nextSection &&
+            mapping.generatedLine === nextSection.generatedOffset.generatedLine
+          ) {
+            mapping.lastGeneratedColumn =
+              nextSection.generatedOffset.generatedColumn - 2;
+          }
+          mapping.generatedLine += lineShift;
+
+          aCallback.call(this, mapping);
+        },
+        aContext,
+        aOrder
+      );
+    });
+  }
+
+  computeColumnSpans() {
+    for (let i = 0; i < this._sections.length; i++) {
+      this._sections[i].consumer.computeColumnSpans();
+    }
+  }
+
+  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/devtools/client/shared/vendor/source-map/lib/source-map-generator.js b/devtools/client/shared/vendor/source-map/lib/source-map-generator.js
new file mode 100644
index 0000000000..847017fac6
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/source-map-generator.js
@@ -0,0 +1,439 @@
+/* -*- 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
+ */
+
+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
+ * being built incrementally. You may pass an object with the following
+ * properties:
+ *
+ *   - file: The filename of the generated source.
+ *   - sourceRoot: A root for all relative URLs in this source map.
+ */
+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;
+  }
+
+  /**
+   * 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,
+    });
+    aSourceMapConsumer.eachMapping(function (mapping) {
+      const newMapping = {
+        generated: {
+          line: mapping.generatedLine,
+          column: mapping.generatedColumn,
+        },
+      };
+
+      if (mapping.source != null) {
+        newMapping.source = mapping.source;
+        if (sourceRoot != null) {
+          newMapping.source = util.relative(sourceRoot, newMapping.source);
+        }
+
+        newMapping.original = {
+          line: mapping.originalLine,
+          column: mapping.originalColumn,
+        };
+
+        if (mapping.name != null) {
+          newMapping.name = mapping.name;
+        }
+      }
+
+      generator.addMapping(newMapping);
+    });
+    aSourceMapConsumer.sources.forEach(function (sourceFile) {
+      let sourceRelative = sourceFile;
+      if (sourceRoot != null) {
+        sourceRelative = util.relative(sourceRoot, sourceFile);
+      }
+
+      if (!generator._sources.has(sourceRelative)) {
+        generator._sources.add(sourceRelative);
+      }
+
+      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.
+   */
+  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);
+    }
+
+    if (source != null) {
+      source = String(source);
+      if (!this._sources.has(source)) {
+        this._sources.add(source);
+      }
+    }
+
+    if (name != null) {
+      name = String(name);
+      if (!this._names.has(name)) {
+        this._names.add(name);
+      }
+    }
+
+    this._mappings.add({
+      generatedLine: generated.line,
+      generatedColumn: generated.column,
+      originalLine: original && original.line,
+      originalColumn: original && original.column,
+      source,
+      name,
+    });
+  }
+
+  /**
+   * Set the source content for a source file.
+   */
+  setSourceContent(aSourceFile, aSourceContent) {
+    let source = aSourceFile;
+    if (this._sourceRoot != null) {
+      source = util.relative(this._sourceRoot, source);
+    }
+
+    if (aSourceContent != null) {
+      // Add the source content to the _sourcesContents map.
+      // Create a new _sourcesContents map if the property is null.
+      if (!this._sourcesContents) {
+        this._sourcesContents = Object.create(null);
+      }
+      this._sourcesContents[util.toSetString(source)] = aSourceContent;
+    } else if (this._sourcesContents) {
+      // Remove the source file from the _sourcesContents map.
+      // If the _sourcesContents map is empty, set the property to null.
+      delete this._sourcesContents[util.toSetString(source)];
+      if (Object.keys(this._sourcesContents).length === 0) {
+        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.
+   */
+  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, " +
+            'or the source map\'s "file" property. Both were omitted.'
+        );
+      }
+      sourceFile = aSourceMapConsumer.file;
+    }
+    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.
+    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) {
+      if (mapping.source === sourceFile && mapping.originalLine != null) {
+        // Check if it can be mapped by the source map, then update the mapping.
+        const original = aSourceMapConsumer.originalPositionFor({
+          line: mapping.originalLine,
+          column: mapping.originalColumn,
+        });
+        if (original.source != null) {
+          // Copy mapping
+          mapping.source = original.source;
+          if (aSourceMapPath != null) {
+            mapping.source = util.join(aSourceMapPath, mapping.source);
+          }
+          if (sourceRoot != null) {
+            mapping.source = util.relative(sourceRoot, mapping.source);
+          }
+          mapping.originalLine = original.line;
+          mapping.originalColumn = original.column;
+          if (original.name != null) {
+            mapping.name = original.name;
+          }
+        }
+      }
+
+      const source = mapping.source;
+      if (source != null && !newSources.has(source)) {
+        newSources.add(source);
+      }
+
+      const name = mapping.name;
+      if (name != null && !newNames.has(name)) {
+        newNames.add(name);
+      }
+    }, this);
+    this._sources = newSources;
+    this._names = newNames;
+
+    // Copy sourcesContents of applied map.
+    aSourceMapConsumer.sources.forEach(function (srcFile) {
+      const content = aSourceMapConsumer.sourceContentFor(srcFile);
+      if (content != null) {
+        if (aSourceMapPath != null) {
+          srcFile = util.join(aSourceMapPath, srcFile);
+        }
+        if (sourceRoot != null) {
+          srcFile = util.relative(sourceRoot, srcFile);
+        }
+        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.
+   */
+  _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"
+    ) {
+      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."
+      );
+    }
+
+    if (
+      aGenerated &&
+      "line" in aGenerated &&
+      "column" in aGenerated &&
+      aGenerated.line > 0 &&
+      aGenerated.column >= 0 &&
+      !aOriginal &&
+      !aSource &&
+      !aName
+    ) {
+      // Case 1.
+    } 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.
+    } 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.
+   */
+  _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 = "";
+
+      if (mapping.generatedLine !== previousGeneratedLine) {
+        previousGeneratedColumn = 0;
+        while (mapping.generatedLine !== previousGeneratedLine) {
+          next += ";";
+          previousGeneratedLine++;
+        }
+      } else if (i > 0) {
+        if (
+          !util.compareByGeneratedPositionsInflated(mapping, mappings[i - 1])
+        ) {
+          continue;
+        }
+        next += ",";
+      }
+
+      next += base64VLQ.encode(
+        mapping.generatedColumn - previousGeneratedColumn
+      );
+      previousGeneratedColumn = mapping.generatedColumn;
+
+      if (mapping.source != null) {
+        sourceIdx = this._sources.indexOf(mapping.source);
+        next += base64VLQ.encode(sourceIdx - previousSource);
+        previousSource = sourceIdx;
+
+        // lines are stored 0-based in SourceMap spec version 3
+        next += base64VLQ.encode(
+          mapping.originalLine - 1 - previousOriginalLine
+        );
+        previousOriginalLine = mapping.originalLine - 1;
+
+        next += base64VLQ.encode(
+          mapping.originalColumn - previousOriginalColumn
+        );
+        previousOriginalColumn = mapping.originalColumn;
+
+        if (mapping.name != null) {
+          nameIdx = this._names.indexOf(mapping.name);
+          next += base64VLQ.encode(nameIdx - previousName);
+          previousName = nameIdx;
+        }
+      }
+
+      result += next;
+    }
+
+    return result;
+  }
+
+  _generateSourcesContent(aSources, aSourceRoot) {
+    return aSources.map(function (source) {
+      if (!this._sourcesContents) {
+        return null;
+      }
+      if (aSourceRoot != null) {
+        source = util.relative(aSourceRoot, source);
+      }
+      const key = util.toSetString(source);
+      return Object.prototype.hasOwnProperty.call(this._sourcesContents, key)
+        ? this._sourcesContents[key]
+        : null;
+    }, this);
+  }
+
+  /**
+   * Externalize the source map.
+   */
+  toJSON() {
+    const map = {
+      version: this._version,
+      sources: this._sources.toArray(),
+      names: this._names.toArray(),
+      mappings: this._serializeMappings(),
+    };
+    if (this._file != null) {
+      map.file = this._file;
+    }
+    if (this._sourceRoot != null) {
+      map.sourceRoot = this._sourceRoot;
+    }
+    if (this._sourcesContents) {
+      map.sourcesContent = this._generateSourcesContent(
+        map.sources,
+        map.sourceRoot
+      );
+    }
+
+    return map;
+  }
+
+  /**
+   * 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/devtools/client/shared/vendor/source-map/lib/source-node.js b/devtools/client/shared/vendor/source-map/lib/source-node.js
new file mode 100644
index 0000000000..ecee1ae620
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/source-node.js
@@ -0,0 +1,430 @@
+/* -*- 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
+ */
+
+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).
+const REGEX_NEWLINE = /(\r?\n)/;
+
+// Newline character code for charCodeAt() comparisons
+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!
+const isSourceNode = "$$$isSourceNode$$$";
+
+/**
+ * SourceNodes provide a way to abstract over interpolating/concatenating
+ * snippets of generated JavaScript source code while maintaining the line and
+ * column information associated with the original source code.
+ *
+ * @param aLine The original line number.
+ * @param aColumn The original column number.
+ * @param aSource The original source's filename.
+ * @param aChunks Optional. An array of strings which are snippets of
+ *        generated JS, or other SourceNodes.
+ * @param aName The original identifier.
+ */
+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.
+   */
+  static fromStringWithSourceMap(
+    aGeneratedCode,
+    aSourceMapConsumer,
+    aRelativePath
+  ) {
+    // The SourceNode we want to fill with the generated code
+    // and the SourceMap
+    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`.
+    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.
+      const newLine = getNextLine() || "";
+      return lineContents + newLine;
+
+      function getNextLine() {
+        return remainingLinesIndex < remainingLines.length
+          ? remainingLines[remainingLinesIndex++]
+          : undefined;
+      }
+    };
+
+    // We need to remember the position of "remainingLines"
+    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.
+    let lastMapping = null;
+    let nextLine;
+
+    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.
+        if (lastGeneratedLine < mapping.generatedLine) {
+          // Associate first line with "lastMapping"
+          addMappingWithCode(lastMapping, shiftNextLine());
+          lastGeneratedLine++;
+          lastGeneratedColumn = 0;
+          // The remaining code is added without mapping
+        } else {
+          // There is no new line in between.
+          // Associate the code between "lastGeneratedColumn" and
+          // "mapping.generatedColumn" with "lastMapping"
+          nextLine = remainingLines[remainingLinesIndex] || "";
+          const code = nextLine.substr(
+            0,
+            mapping.generatedColumn - lastGeneratedColumn
+          );
+          remainingLines[remainingLinesIndex] = nextLine.substr(
+            mapping.generatedColumn - lastGeneratedColumn
+          );
+          lastGeneratedColumn = mapping.generatedColumn;
+          addMappingWithCode(lastMapping, code);
+          // No more remaining code, continue
+          lastMapping = mapping;
+          return;
+        }
+      }
+      // We add the generated code until the first mapping
+      // to the SourceNode without any mapping.
+      // Each line is added as separate string.
+      while (lastGeneratedLine < mapping.generatedLine) {
+        node.add(shiftNextLine());
+        lastGeneratedLine++;
+      }
+      if (lastGeneratedColumn < mapping.generatedColumn) {
+        nextLine = remainingLines[remainingLinesIndex] || "";
+        node.add(nextLine.substr(0, mapping.generatedColumn));
+        remainingLines[remainingLinesIndex] = nextLine.substr(
+          mapping.generatedColumn
+        );
+        lastGeneratedColumn = mapping.generatedColumn;
+      }
+      lastMapping = mapping;
+    }, this);
+    // We have processed all mappings.
+    if (remainingLinesIndex < remainingLines.length) {
+      if (lastMapping) {
+        // Associate the remaining code in the current line with "lastMapping"
+        addMappingWithCode(lastMapping, shiftNextLine());
+      }
+      // and add the remaining lines without any mapping
+      node.add(remainingLines.splice(remainingLinesIndex).join(""));
+    }
+
+    // Copy sourcesContent into SourceNode
+    aSourceMapConsumer.sources.forEach(function (sourceFile) {
+      const content = aSourceMapConsumer.sourceContentFor(sourceFile);
+      if (content != null) {
+        if (aRelativePath != null) {
+          sourceFile = util.join(aRelativePath, sourceFile);
+        }
+        node.setSourceContent(sourceFile, content);
+      }
+    });
+
+    return node;
+
+    function addMappingWithCode(mapping, code) {
+      if (mapping === null || mapping.source === undefined) {
+        node.add(code);
+      } else {
+        const source = aRelativePath
+          ? util.join(aRelativePath, mapping.source)
+          : mapping.source;
+        node.add(
+          new SourceNode(
+            mapping.originalLine,
+            mapping.originalColumn,
+            source,
+            code,
+            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.
+   */
+  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;
+  }
+
+  /**
+   * 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;
+  }
+
+  /**
+   * 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,
+        });
+      }
+    }
+  }
+
+  /**
+   * 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]);
+      this.children = newChildren;
+    }
+    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.
+   */
+  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;
+  }
+
+  /**
+   * 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.
+   */
+  walkSourceContents(aFn) {
+    for (let i = 0, len = this.children.length; i < len; i++) {
+      if (this.children[i][isSourceNode]) {
+        this.children[i].walkSourceContents(aFn);
+      }
+    }
+
+    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.
+   */
+  toString() {
+    let str = "";
+    this.walk(function (chunk) {
+      str += chunk;
+    });
+    return str;
+  }
+
+  /**
+   * 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: {
+              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 (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 };
+  }
+}
+
+exports.SourceNode = SourceNode;
diff --git a/devtools/client/shared/vendor/source-map/lib/url.js b/devtools/client/shared/vendor/source-map/lib/url.js
new file mode 100644
index 0000000000..b0f4434fe5
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/url.js
@@ -0,0 +1,21 @@
+/* -*- 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
+ */
+"use strict";
+
+/**
+ * Browser 'URL' implementations have been found to handle non-standard URL
+ * schemes poorly, and schemes like
+ *
+ *   webpack:///src/folder/file.js
+ *
+ * are very common in source maps. For the time being we use a JS
+ * implementation in these contexts instead. See
+ *
+ * * https://bugzilla.mozilla.org/show_bug.cgi?id=1374505
+ * * https://bugs.chromium.org/p/chromium/issues/detail?id=734880
+ */
+module.exports = require("../../whatwg-url.js").URL;
diff --git a/devtools/client/shared/vendor/source-map/lib/util.js b/devtools/client/shared/vendor/source-map/lib/util.js
new file mode 100644
index 0000000000..20fe8f6859
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/util.js
@@ -0,0 +1,444 @@
+/* -*- 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
+ */
+
+const URL = require("./url");
+
+/**
+ * This is a helper function for getting values from parameter/options
+ * objects.
+ *
+ * @param args The object we are extracting values from
+ * @param name The name of the property we are getting.
+ * @param defaultValue An optional value to return if the property is missing
+ * from the object. If this is not specified and the property is missing, an
+ * error will be thrown.
+ */
+function getArg(aArgs, aName, aDefaultValue) {
+  if (aName in aArgs) {
+    return aArgs[aName];
+  } else if (arguments.length === 3) {
+    return aDefaultValue;
+  }
+  throw new Error('"' + aName + '" is a required argument.');
+}
+exports.getArg = getArg;
+
+const supportsNullProto = (function () {
+  const obj = Object.create(null);
+  return !("__proto__" in obj);
+})();
+
+function identity(s) {
+  return s;
+}
+
+/**
+ * Because behavior goes wacky when you set `__proto__` on objects, we
+ * have to prefix all the strings in our set with an arbitrary character.
+ *
+ * See https://github.com/mozilla/source-map/pull/31 and
+ * https://github.com/mozilla/source-map/issues/30
+ *
+ * @param String aStr
+ */
+function toSetString(aStr) {
+  if (isProtoString(aStr)) {
+    return "$" + aStr;
+  }
+
+  return aStr;
+}
+exports.toSetString = supportsNullProto ? identity : toSetString;
+
+function fromSetString(aStr) {
+  if (isProtoString(aStr)) {
+    return aStr.slice(1);
+  }
+
+  return aStr;
+}
+exports.fromSetString = supportsNullProto ? identity : fromSetString;
+
+function isProtoString(s) {
+  if (!s) {
+    return false;
+  }
+
+  const length = s.length;
+
+  if (length < 9 /* "__proto__".length */) {
+    return false;
+  }
+
+  /* eslint-disable no-multi-spaces */
+  if (
+    s.charCodeAt(length - 1) !== 95 /* '_' */ ||
+    s.charCodeAt(length - 2) !== 95 /* '_' */ ||
+    s.charCodeAt(length - 3) !== 111 /* 'o' */ ||
+    s.charCodeAt(length - 4) !== 116 /* 't' */ ||
+    s.charCodeAt(length - 5) !== 111 /* 'o' */ ||
+    s.charCodeAt(length - 6) !== 114 /* 'r' */ ||
+    s.charCodeAt(length - 7) !== 112 /* 'p' */ ||
+    s.charCodeAt(length - 8) !== 95 /* '_' */ ||
+    s.charCodeAt(length - 9) !== 95 /* '_' */
+  ) {
+    return false;
+  }
+  /* eslint-enable no-multi-spaces */
+
+  for (let i = length - 10; i >= 0; i--) {
+    if (s.charCodeAt(i) !== 36 /* '$' */) {
+      return false;
+    }
+  }
+
+  return true;
+}
+
+function strcmp(aStr1, aStr2) {
+  if (aStr1 === aStr2) {
+    return 0;
+  }
+
+  if (aStr1 === null) {
+    return 1; // aStr2 !== null
+  }
+
+  if (aStr2 === null) {
+    return -1; // aStr1 !== null
+  }
+
+  if (aStr1 > aStr2) {
+    return 1;
+  }
+
+  return -1;
+}
+
+/**
+ * Comparator between two mappings with inflated source and name strings where
+ * the generated positions are compared.
+ */
+function compareByGeneratedPositionsInflated(mappingA, mappingB) {
+  let cmp = mappingA.generatedLine - mappingB.generatedLine;
+  if (cmp !== 0) {
+    return cmp;
+  }
+
+  cmp = mappingA.generatedColumn - mappingB.generatedColumn;
+  if (cmp !== 0) {
+    return cmp;
+  }
+
+  cmp = strcmp(mappingA.source, mappingB.source);
+  if (cmp !== 0) {
+    return cmp;
+  }
+
+  cmp = mappingA.originalLine - mappingB.originalLine;
+  if (cmp !== 0) {
+    return cmp;
+  }
+
+  cmp = mappingA.originalColumn - mappingB.originalColumn;
+  if (cmp !== 0) {
+    return cmp;
+  }
+
+  return strcmp(mappingA.name, mappingB.name);
+}
+exports.compareByGeneratedPositionsInflated =
+  compareByGeneratedPositionsInflated;
+
+/**
+ * Strip any JSON XSSI avoidance prefix from the string (as documented
+ * in the source maps specification), and then parse the string as
+ * JSON.
+ */
+function parseSourceMapInput(str) {
+  return JSON.parse(str.replace(/^\)]}'[^\n]*\n/, ""));
+}
+exports.parseSourceMapInput = parseSourceMapInput;
+
+// We use 'http' as the base here because we want URLs processed relative
+// to the safe base to be treated as "special" URLs during parsing using
+// the WHATWG URL parsing. This ensures that backslash normalization
+// applies to the path and such.
+const PROTOCOL = "http:";
+const PROTOCOL_AND_HOST = `${PROTOCOL}//host`;
+
+/**
+ * Make it easy to create small utilities that tweak a URL's path.
+ */
+function createSafeHandler(cb) {
+  return input => {
+    const type = getURLType(input);
+    const base = buildSafeBase(input);
+    const url = new URL(input, base);
+
+    cb(url);
+
+    const result = url.toString();
+
+    if (type === "absolute") {
+      return result;
+    } else if (type === "scheme-relative") {
+      return result.slice(PROTOCOL.length);
+    } else if (type === "path-absolute") {
+      return result.slice(PROTOCOL_AND_HOST.length);
+    }
+
+    // This assumes that the callback will only change
+    // the path, search and hash values.
+    return computeRelativeURL(base, result);
+  };
+}
+
+function withBase(url, base) {
+  return new URL(url, base).toString();
+}
+
+function buildUniqueSegment(prefix, str) {
+  let id = 0;
+  do {
+    const ident = prefix + id++;
+    if (str.indexOf(ident) === -1) return ident;
+  } while (true);
+}
+
+function buildSafeBase(str) {
+  const maxDotParts = str.split("..").length - 1;
+
+  // If we used a segment that also existed in `str`, then we would be unable
+  // to compute relative paths. For example, if `segment` were just "a":
+  //
+  //   const url = "../../a/"
+  //   const base = buildSafeBase(url); // http://host/a/a/
+  //   const joined = "http://host/a/";
+  //   const result = relative(base, joined);
+  //
+  // Expected: "../../a/";
+  // Actual: "a/"
+  //
+  const segment = buildUniqueSegment("p", str);
+
+  let base = `${PROTOCOL_AND_HOST}/`;
+  for (let i = 0; i < maxDotParts; i++) {
+    base += `${segment}/`;
+  }
+  return base;
+}
+
+const ABSOLUTE_SCHEME = /^[A-Za-z0-9\+\-\.]+:/;
+function getURLType(url) {
+  if (url[0] === "/") {
+    if (url[1] === "/") return "scheme-relative";
+    return "path-absolute";
+  }
+
+  return ABSOLUTE_SCHEME.test(url) ? "absolute" : "path-relative";
+}
+
+/**
+ * Given two URLs that are assumed to be on the same
+ * protocol/host/user/password build a relative URL from the
+ * path, params, and hash values.
+ *
+ * @param rootURL The root URL that the target will be relative to.
+ * @param targetURL The target that the relative URL points to.
+ * @return A rootURL-relative, normalized URL value.
+ */
+function computeRelativeURL(rootURL, targetURL) {
+  if (typeof rootURL === "string") rootURL = new URL(rootURL);
+  if (typeof targetURL === "string") targetURL = new URL(targetURL);
+
+  const targetParts = targetURL.pathname.split("/");
+  const rootParts = rootURL.pathname.split("/");
+
+  // If we've got a URL path ending with a "/", we remove it since we'd
+  // otherwise be relative to the wrong location.
+  if (rootParts.length > 0 && !rootParts[rootParts.length - 1]) {
+    rootParts.pop();
+  }
+
+  while (
+    targetParts.length > 0 &&
+    rootParts.length > 0 &&
+    targetParts[0] === rootParts[0]
+  ) {
+    targetParts.shift();
+    rootParts.shift();
+  }
+
+  const relativePath = rootParts
+    .map(() => "..")
+    .concat(targetParts)
+    .join("/");
+
+  return relativePath + targetURL.search + targetURL.hash;
+}
+
+/**
+ * Given a URL, ensure that it is treated as a directory URL.
+ *
+ * @param url
+ * @return A normalized URL value.
+ */
+const ensureDirectory = createSafeHandler(url => {
+  url.pathname = url.pathname.replace(/\/?$/, "/");
+});
+
+/**
+ * Given a URL, strip off any filename if one is present.
+ *
+ * @param url
+ * @return A normalized URL value.
+ */
+const trimFilename = createSafeHandler(url => {
+  url.href = new URL(".", url.toString()).toString();
+});
+
+/**
+ * Normalize a given URL.
+ * * Convert backslashes.
+ * * Remove any ".." and "." segments.
+ *
+ * @param url
+ * @return A normalized URL value.
+ */
+const normalize = createSafeHandler(url => {});
+exports.normalize = normalize;
+
+/**
+ * Joins two paths/URLs.
+ *
+ * All returned URLs will be normalized.
+ *
+ * @param aRoot The root path or URL. Assumed to reference a directory.
+ * @param aPath The path or URL to be joined with the root.
+ * @return A joined and normalized URL value.
+ */
+function join(aRoot, aPath) {
+  const pathType = getURLType(aPath);
+  const rootType = getURLType(aRoot);
+
+  aRoot = ensureDirectory(aRoot);
+
+  if (pathType === "absolute") {
+    return withBase(aPath, undefined);
+  }
+  if (rootType === "absolute") {
+    return withBase(aPath, aRoot);
+  }
+
+  if (pathType === "scheme-relative") {
+    return normalize(aPath);
+  }
+  if (rootType === "scheme-relative") {
+    return withBase(aPath, withBase(aRoot, PROTOCOL_AND_HOST)).slice(
+      PROTOCOL.length
+    );
+  }
+
+  if (pathType === "path-absolute") {
+    return normalize(aPath);
+  }
+  if (rootType === "path-absolute") {
+    return withBase(aPath, withBase(aRoot, PROTOCOL_AND_HOST)).slice(
+      PROTOCOL_AND_HOST.length
+    );
+  }
+
+  const base = buildSafeBase(aPath + aRoot);
+  const newPath = withBase(aPath, withBase(aRoot, base));
+  return computeRelativeURL(base, newPath);
+}
+exports.join = join;
+
+/**
+ * Make a path relative to a URL or another path. If returning a
+ * relative URL is not possible, the original target will be returned.
+ * All returned URLs will be normalized.
+ *
+ * @param aRoot The root path or URL.
+ * @param aPath The path or URL to be made relative to aRoot.
+ * @return A rootURL-relative (if possible), normalized URL value.
+ */
+function relative(rootURL, targetURL) {
+  const result = relativeIfPossible(rootURL, targetURL);
+
+  return typeof result === "string" ? result : normalize(targetURL);
+}
+exports.relative = relative;
+
+function relativeIfPossible(rootURL, targetURL) {
+  const urlType = getURLType(rootURL);
+  if (urlType !== getURLType(targetURL)) {
+    return null;
+  }
+
+  const base = buildSafeBase(rootURL + targetURL);
+  const root = new URL(rootURL, base);
+  const target = new URL(targetURL, base);
+
+  try {
+    new URL("", target.toString());
+  } catch (err) {
+    // Bail if the URL doesn't support things being relative to it,
+    // For example, data: and blob: URLs.
+    return null;
+  }
+
+  if (
+    target.protocol !== root.protocol ||
+    target.user !== root.user ||
+    target.password !== root.password ||
+    target.hostname !== root.hostname ||
+    target.port !== root.port
+  ) {
+    return null;
+  }
+
+  return computeRelativeURL(root, target);
+}
+
+/**
+ * Compute the URL of a source given the the source root, the source's
+ * URL, and the source map's URL.
+ */
+function computeSourceURL(sourceRoot, sourceURL, sourceMapURL) {
+  // The source map spec states that "sourceRoot" and "sources" entries are to be appended. While
+  // that is a little vague, implementations have generally interpreted that as joining the
+  // URLs with a `/` between then, assuming the "sourceRoot" doesn't already end with one.
+  // For example,
+  //
+  //   sourceRoot: "some-dir",
+  //   sources: ["/some-path.js"]
+  //
+  // and
+  //
+  //   sourceRoot: "some-dir/",
+  //   sources: ["/some-path.js"]
+  //
+  // must behave as "some-dir/some-path.js".
+  //
+  // With this library's the transition to a more URL-focused implementation, that behavior is
+  // preserved here. To acheive that, we trim the "/" from absolute-path when a sourceRoot value
+  // is present in order to make the sources entries behave as if they are relative to the
+  // "sourceRoot", as they would have if the two strings were simply concated.
+  if (sourceRoot && getURLType(sourceURL) === "path-absolute") {
+    sourceURL = sourceURL.replace(/^\//, "");
+  }
+
+  let url = normalize(sourceURL || "");
+
+  // Parsing URLs can be expensive, so we only perform these joins when needed.
+  if (sourceRoot) url = join(sourceRoot, url);
+  if (sourceMapURL) url = join(trimFilename(sourceMapURL), url);
+  return url;
+}
+exports.computeSourceURL = computeSourceURL;
diff --git a/devtools/client/shared/vendor/source-map/lib/wasm.js b/devtools/client/shared/vendor/source-map/lib/wasm.js
new file mode 100644
index 0000000000..3091d9ee26
--- /dev/null
+++ b/devtools/client/shared/vendor/source-map/lib/wasm.js
@@ -0,0 +1,138 @@
+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;
+};