Make GetRootWindow() return a Window instead of a RootWindow.

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/caps_lock_delegate_stub.h"
 #include "ash/default_accessibility_delegate.h"
 #include "ash/default_user_wallpaper_delegate.h"
@@ skipping 134 matching lines @@
 
 void ShellDelegateImpl::HandleMediaNextTrack() {
 }
 
 void ShellDelegateImpl::HandleMediaPlayPause() {
 }
 
 void ShellDelegateImpl::HandleMediaPrevTrack() {
 }
 
-ui::MenuModel* ShellDelegateImpl::CreateContextMenu(aura::RootWindow* root) {
+ui::MenuModel* ShellDelegateImpl::CreateContextMenu(aura::Window* root) {
   return new ContextMenu(root);
 }
 
 RootWindowHostFactory* ShellDelegateImpl::CreateRootWindowHostFactory() {
   return RootWindowHostFactory::Create();
 }
 
 base::string16 ShellDelegateImpl::GetProductName() const {
   return base::string16();
 }
 
 }  // namespace shell
 }  // namespace ash