ash: Do not use MessageLoopForUI when not needed.

ash/shell/shell_delegate_impl.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 "ash/shell/shell_delegate_impl.h"
 
 #include "ash/accessibility_delegate.h"
 #include "ash/default_accessibility_delegate.h"
 #include "ash/default_user_wallpaper_delegate.h"
 #include "ash/gpu_support_stub.h"
@@ skipping 154 matching lines @@
   return false;
 }
 
 void ShellDelegateImpl::PreInit() {
 }
 
 void ShellDelegateImpl::PreShutdown() {
 }
 
 void ShellDelegateImpl::Exit() {
-  base::MessageLoopForUI::current()->QuitWhenIdle();
+  base::MessageLoop::current()->QuitWhenIdle();
 }
 
 keyboard::KeyboardUI* ShellDelegateImpl::CreateKeyboardUI() {
   return new TestKeyboardUI;
 }
 
 void ShellDelegateImpl::VirtualKeyboardActivated(bool activated) {
 }
 
 void ShellDelegateImpl::AddVirtualKeyboardStateObserver(
@@ skipping 54 matching lines @@
 base::string16 ShellDelegateImpl::GetProductName() const {
   return base::string16();
 }
 
 gfx::Image ShellDelegateImpl::GetDeprecatedAcceleratorImage() const {
   return gfx::Image();
 }
 
 }  // namespace shell
 }  // namespace ash