Add base::RunLoop and update ui_test_utils to use it to reduce flakiness

chrome/test/base/test_web_dialog_observer.h

 // 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.
 
 #ifndef CHROME_TEST_BASE_TEST_WEB_DIALOG_OBSERVER_H_
 #define CHROME_TEST_BASE_TEST_WEB_DIALOG_OBSERVER_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "chrome/test/base/ui_test_utils.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "ui/web_dialogs/web_dialog_observer.h"
 
 
 namespace content {
 class JsInjectionReadyObserver;
 class RenderViewHost;
 class WebUI;
 }
@@ skipping 27 matching lines @@
                        const content::NotificationDetails& details) OVERRIDE;
 
   content::NotificationRegistrar registrar_;
 
   // Observer to take some action when the dialog is ready for JavaScript
   // injection.
   content::JsInjectionReadyObserver* js_injection_ready_observer_;
   content::WebUI* web_ui_;
   bool done_;
   bool running_;
+  scoped_refptr<ui_test_utils::MessageLoopRunner> message_loop_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(TestWebDialogObserver);
 };
 
 #endif  // CHROME_TEST_BASE_TEST_WEB_DIALOG_OBSERVER_H_