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

ui/aura/env.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 UI_AURA_ENV_H_
 #define UI_AURA_ENV_H_
 #pragma once
 
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop.h"
@@ skipping 50 matching lines @@
   MonitorManager* monitor_manager() { return monitor_manager_.get(); }
   void SetMonitorManager(MonitorManager* monitor_manager);
 
   // Env takes ownership of the EventFilter.
   EventFilter* event_filter() { return event_filter_.get(); }
   void SetEventFilter(EventFilter* event_filter);
 
   CursorManager* cursor_manager() { return &cursor_manager_; }
 
   // Returns the native event dispatcher. The result should only be passed to
-  // MessageLoopForUI::RunWithDispatcher() or
-  // MessageLoopForUI::RunAllPendingWithDispatcher(), or used to dispatch
-  // an event by |Dispatch(const NativeEvent&)| on it. It must never be stored.
+  // base::RunLoop(dispatcher), or used to dispatch an event by
+  // |Dispatch(const NativeEvent&)| on it. It must never be stored.
 #if !defined(OS_MACOSX)
   MessageLoop::Dispatcher* GetDispatcher();
 #endif
 
  private:
   friend class Window;
 
   void Init();
 
   // Called by the Window when it is initialized. Notifies observers.
@@ skipping 15 matching lines @@
 #if defined(USE_X11)
   scoped_ptr<internal::MonitorChangeObserverX11> monitor_change_observer_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(Env);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_ENV_H_