WebUI: Allow rejecting a promise that is returned from cr.sendWithPromise().

ui/webui/resources/js/cr.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.
 
 /**
  * The global object.
  * @type {!Object}
  * @const
  */
 var global = this;
 
 /** @typedef {{eventName: string, uid: number}} */
 var WebUIListener;
 
 /** Platform, package, object property, and Event support. **/
-var cr = function() {
+var cr = cr || function() {

[dpapad, 2016/03/02 19:14:55]

Every time cr.js is evaluated is overwriting anything that has been previously
defined on 'cr' namespace. For example what is happening in my case (left the
console.logs on purpose to showcase the problem).

To reproduce do the following
1) Revert this line here.
2) ./out/Default_gn/browser_tests
--gtest_filter=CrSettingsSearchEnginesTest.SearchEngines

You will see the following in the output
cr.js running
promise_resolver.js running
cr.js running // overwrites the 'cr' namespace and cr.PromiseResolver no longer
exists.
<test is failing because cr.PromiseResolver> does not exist.

With this change, the 2nd time cr.js is evaluated does nothing, and no
overwriting happens, fixing the issue.

   'use strict';
 
   /**
    * Builds an object structure for the provided namespace path,
    * ensuring that names that already exist are not overwritten. For
    * example:
    * "a.b.c" -> a = {};a.b={};a.b.c={};
    * @param {string} name Name of the object that this file defines.
    * @param {*=} opt_object The object to expose at the end of the path.
    * @param {Object=} opt_objectToExportTo The object to add the path to;
@@ skipping 388 matching lines @@
   function removeWebUIListener(listener) {
     var listenerExists = webUIListenerMap[listener.eventName] &&
         webUIListenerMap[listener.eventName][listener.uid];
     if (listenerExists) {
       delete webUIListenerMap[listener.eventName][listener.uid];
       return true;
     }
     return false;
   }
 
+  console.log('cr.js running');
   return {
     addSingletonGetter: addSingletonGetter,
     createUid: createUid,
     define: define,
     defineProperty: defineProperty,
     dispatchPropertyChange: dispatchPropertyChange,
     dispatchSimpleEvent: dispatchSimpleEvent,
     exportPath: exportPath,
     getUid: getUid,
     makePublic: makePublic,
@@ skipping 29 matching lines @@
     get isLinux() {
       return /Linux/.test(navigator.userAgent);
     },
 
     /** Whether this is on Android. */
     get isAndroid() {
       return /Android/.test(navigator.userAgent);
     }
   };
 }();