DevTools: use diff_match_patch instead of jsdifflib for text diffing.

Source/devtools/front_end/externs.js

 /*
  * Copyright (C) 2011 Google Inc. 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
@@ skipping 289 matching lines @@
 }
 
 var Adb = {};
 /** @typedef {{id: string, name: string, url: string, adbAttachedForeign: boolean}} */
 Adb.Page;
 /** @typedef {{id: string, adbBrowserChromeVersion: string, compatibleVersion: boolean, adbBrowserName: string, source: string, adbBrowserVersion: string, pages: !Array<!Adb.Page>}} */
 Adb.Browser;
 /** @typedef {{id: string, adbModel: string, adbSerial: string, browsers: !Array.<!Adb.Browser>, adbPortStatus: !Array.<number>, adbConnected: boolean}} */
 Adb.Device;
 
-/* jsdifflib API */
-var difflib = {};
-difflib.stringAsLines = function(text) { return []; }
-/** @constructor */
-difflib.SequenceMatcher = function(baseText, newText) { }
-difflib.SequenceMatcher.prototype.get_opcodes = function() { return []; }
+/**
+ * @constructor
+ */
+function diff_match_patch()
+{
+}
+
+diff_match_patch.prototype = {
+    /**
+     * @param {string} text1
+     * @param {string} text2
+     * @return {!Array.<!{0: number, 1: string}>}
+     */
+    diff_main: function(text1, text2) { }
+}
 
 /** @constructor */
 function Path2D() {}
 Path2D.prototype = {
     /**
      * @param {number} x
      * @param {number} y
      * @param {number} w
      * @param {number} h
      */
@@ skipping 333 matching lines @@
  * @extends {ESTree.Node}
  * @constructor
  */
 ESTree.TemplateLiteralNode = function()
 {
     /** @type {!Array.<!ESTree.Node>} */
     this.quasis;
     /** @type {!Array.<!ESTree.Node>} */
     this.expressions;
 }