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

ash/shell/window_watcher_launcher_item_delegate.cc

 // Copyright 2013 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/window_watcher_launcher_item_delegate.h"
 
 #include "ash/shell/window_watcher.h"
 #include "ash/wm/window_util.h"
 #include "ui/aura/window.h"
 
@@ skipping 18 matching lines @@
     ash::wm::MoveWindowToEventRoot(window, event);
   window->Show();
   ash::wm::ActivateWindow(window);
 }
 
 base::string16 WindowWatcherLauncherItemDelegate::GetTitle() {
   return watcher_->GetWindowByID(id_)->title();
 }
 
 ui::MenuModel* WindowWatcherLauncherItemDelegate::CreateContextMenu(
-    aura::RootWindow* root_window) {
+    aura::Window* root_window) {
   return NULL;
 }
 
 ash::LauncherMenuModel*
 WindowWatcherLauncherItemDelegate::CreateApplicationMenu(
     int event_flags) {
   return NULL;
 }
 
 bool WindowWatcherLauncherItemDelegate::IsDraggable() {
   return true;
 }
 
 bool WindowWatcherLauncherItemDelegate::ShouldShowTooltip() {
   return true;
 }
 
 }  // namespace shell
 }  // namespace ash