DevTools: Move jsdifflib to "sources", extract "toolbox" module

Source/devtools/front_end/toolbox/InspectedPagePlaceholder.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @extends {WebInspector.View}
  */
 WebInspector.InspectedPagePlaceholder = function()
 {
@@ skipping 103 matching lines @@
     update: function()
     {
         delete this._updateId;
         var rect = this._dipPageRect();
         var bounds = { x: Math.round(rect.x), y: Math.round(rect.y), height: Math.max(1, Math.round(rect.height)), width: Math.max(1, Math.round(rect.width)) };
         this.dispatchEventToListeners(WebInspector.InspectedPagePlaceholder.Events.Update, bounds);
     },
 
     __proto__: WebInspector.View.prototype
 };