Use the default dispatcher where possible for nested message loops.

ui/views/widget/desktop_aura/desktop_dispatcher_client.cc

 // 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.
 
 #include "ui/views/widget/desktop_aura/desktop_dispatcher_client.h"
 
+#include "base/auto_reset.h"
 #include "base/run_loop.h"
 
 namespace views {
 
 DesktopDispatcherClient::DesktopDispatcherClient() {}
 
 DesktopDispatcherClient::~DesktopDispatcherClient() {}
 
 void DesktopDispatcherClient::RunWithDispatcher(
     base::MessagePumpDispatcher* nested_dispatcher,
     aura::Window* associated_window) {
   // TODO(erg): This class has been copypastad from
   // ash/accelerators/nested_dispatcher_controller.cc. I have left my changes
   // commented out because I don't entirely understand the implications of the
   // change.
   base::MessageLoopForUI* loop = base::MessageLoopForUI::current();
   base::MessageLoopForUI::ScopedNestableTaskAllower allow_nested(loop);
 
   base::RunLoop run_loop(nested_dispatcher);
+  base::AutoReset<base::Closure> reset_closure(&quit_closure_,
+                                               run_loop.QuitClosure());
   run_loop.Run();
 }
 
+void DesktopDispatcherClient::QuitNestedMessageLoop() {
+  CHECK(!quit_closure_.is_null());
+  quit_closure_.Run();
+}
+
 }  // namespace views