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

ash/desktop_background/desktop_background_controller_unittest.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/desktop_background/desktop_background_controller.h"
 
 #include <cmath>
 #include <cstdlib>
 
 #include "ash/ash_switches.h"
@@ skipping 27 matching lines @@
 namespace {
 
 // Containers IDs used for tests.
 const int kDesktopBackgroundId =
     ash::internal::kShellWindowId_DesktopBackgroundContainer;
 const int kLockScreenBackgroundId =
     ash::internal::kShellWindowId_LockScreenBackgroundContainer;
 
 // Returns number of child windows in a shell window container.
 int ChildCountForContainer(int container_id) {
-  RootWindow* root = ash::Shell::GetPrimaryRootWindow();
+  Window* root = ash::Shell::GetPrimaryRootWindow();
   Window* container = root->GetChildById(container_id);
   return static_cast<int>(container->children().size());
 }
 
 class TestObserver : public DesktopBackgroundControllerObserver {
  public:
   explicit TestObserver(DesktopBackgroundController* controller)
       : controller_(controller) {
     DCHECK(controller_);
     controller_->AddObserver(this);
@@ skipping 565 matching lines @@
       DesktopBackgroundController::GetMaxDisplaySizeInNative().ToString());
 
   // Maximum width and height belongs to different displays.
   UpdateDisplay("400x300,100x500");
   EXPECT_EQ(
       "400x500",
       DesktopBackgroundController::GetMaxDisplaySizeInNative().ToString());
 }
 
 }  // namespace ash