Use the default dispatcher where possible for nested message loops.

ui/aura/client/dispatcher_client.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_CLIENT_DISPATCHER_CLIENT_H_
 #define UI_AURA_CLIENT_DISPATCHER_CLIENT_H_
 
 #include "base/message_loop/message_pump_dispatcher.h"
 #include "ui/aura/aura_export.h"
 #include "ui/aura/window.h"
 
 namespace aura {
 class Window;
 namespace client {
 
 // An interface implemented by an object which handles nested dispatchers.
 class AURA_EXPORT DispatcherClient {
  public:
   virtual void RunWithDispatcher(base::MessagePumpDispatcher* dispatcher,
                                  aura::Window* associated_window) = 0;
+
+  virtual void QuitNestedMessageLoop() = 0;
 };
 
 AURA_EXPORT void SetDispatcherClient(Window* root_window,
                                      DispatcherClient* client);
 AURA_EXPORT DispatcherClient* GetDispatcherClient(Window* root_window);
 
 }  // namespace client
 }  // namespace aura
 
 #endif  // UI_AURA_CLIENT_DISPATCHER_CLIENT_H_