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

ui/webui/resources/js/cr.js

Index: ui/webui/resources/js/cr.js
diff --git a/ui/webui/resources/js/cr.js b/ui/webui/resources/js/cr.js
index 10ecb7d210bf69fcc52217cffeebb1242513e565..d68c1102e1cc46efe9ea12f0066630cc2880448f 100644
--- a/ui/webui/resources/js/cr.js
+++ b/ui/webui/resources/js/cr.js
@@ -13,7 +13,7 @@ var global = this;
 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';
 
   /**
@@ -422,6 +422,7 @@ var cr = function() {
     return false;
   }
 
+  console.log('cr.js running');
   return {
     addSingletonGetter: addSingletonGetter,
     createUid: createUid,