Make JS compiler happy about OAUTH2_USE_OFFICEIAL_CLIENT_ID.

remoting/webapp/jscompiler_hacks.js

 // Copyright (c) 2012 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.
 
 // This file contains various hacks needed to inform JSCompiler of various
 // WebKit-specific properties and methods. It is used only with JSCompiler
 // to verify the type-correctness of our code.
 
 /** @type Array.<HTMLElement> */
 Document.prototype.all;
 
 /** @type {function(string): void} */
 Document.prototype.execCommand = function(command) {};
 
 /** @return {void} Nothing. */
 Document.prototype.webkitCancelFullScreen = function() {};
 
 /** @type {boolean} */
 Document.prototype.webkitIsFullScreen;
 
 /** @type {number} */
 Element.ALLOW_KEYBOARD_INPUT;
 
 /** @param {number} flags
 /** @return {void} Nothing. */
 Element.prototype.webkitRequestFullScreen = function(flags) {};
 
 /** @type {{getRandomValues: function(Uint16Array):void}} */
 Window.prototype.crypto;
+
+// This string is replaced with the actual value in build-webapp.py.
+var OAUTH2_USE_OFFICIAL_CLIENT_ID = false;