Increase AsyncExtensionSettingsWebUITest.testDeveloperModeA11y timout.

chrome/browser/ui/webui/extensions/extension_settings_browsertest.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.
 
 // TODO(dbeam): test for loading upacked extensions?
 
 GEN('#include "chrome/browser/ui/webui/extensions/' +
     'extension_settings_browsertest.h"');
 
 /**
@@ skipping 71 matching lines @@
 
   document.addEventListener('webkitTransitionEnd', function f(e) {
     if (e.target == devControl) {
       // Make sure developer controls are not hidden after checkbox is clicked.
       assertFalse(devControl.hidden);
 
       document.removeEventListener(f, 'webkitTransitionEnd');
       testDone();
     }
   });
-  ensureTransitionEndEvent(devControl, 2000);
+  ensureTransitionEndEvent(devControl, 4000);
 });
 
 /**
  * TestFixture for extension settings WebUI testing (commands config edition).
  * @extends {testing.Test}
  * @constructor
  */
 function ExtensionSettingsCommandsConfigWebUITest() {}
 
 ExtensionSettingsCommandsConfigWebUITest.prototype = {
@@ skipping 32 matching lines @@
   testGenPreamble: function() {
     GEN('  InstallGoodExtension();');
   }
 };
 
 TEST_F('ExtensionSettingsWebUITestWithExtensionInstalled',
        'baseAccessibilityIsOk', function() {
   assertEquals(this.browsePreload, document.location.href);
   this.runAccessibilityAudit();
 });