Remove root_window_ member from DesktopBackgroundController.

ash/desktop_background/desktop_background_controller.h

 // 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.
 
 #ifndef ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_
 #define ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_
 #pragma once
 
 #include "ash/ash_export.h"
 #include "ash/desktop_background/desktop_background_resources.h"
@@ skipping 28 matching lines @@
 
 // Loads selected desktop wallpaper from file system asynchronously and updates
 // background layer if loaded successfully.
 class ASH_EXPORT DesktopBackgroundController {
  public:
   enum BackgroundMode {
     BACKGROUND_IMAGE,
     BACKGROUND_SOLID_COLOR
   };
 
-  explicit DesktopBackgroundController(aura::RootWindow* root_window);
+  DesktopBackgroundController();
   virtual ~DesktopBackgroundController();
 
   // Gets the desktop background mode.
   BackgroundMode desktop_background_mode() const {
     return desktop_background_mode_;
   }
 
   // Loads default wallpaper at |index| asynchronously and sets to current
   // wallpaper after loaded.
   void SetDefaultWallpaper(int index);
@@ skipping 24 matching lines @@
 
   // Sets the desktop background to image mode and creates a new background
   // widget with user selected wallpaper or default wallpaper. Deletes the old
   // widget if any.
   void SetDesktopBackgroundImageMode(scoped_refptr<WallpaperOperation> wo);
 
   // Creates a new background widget and sets the background mode to image mode.
   // Called after wallpaper loaded successfully.
   void OnWallpaperLoadCompleted(scoped_refptr<WallpaperOperation> wo);
 
-  aura::RootWindow* root_window_;
-
   // Can change at runtime.
   BackgroundMode desktop_background_mode_;
 
   // The previous successfully loaded wallpaper.
   int previous_index_;
 
   scoped_refptr<WallpaperOperation> wallpaper_op_;
 
   base::WeakPtrFactory<DesktopBackgroundController> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DesktopBackgroundController);
 };
 
 }  // namespace ash
 
 #endif  // ASH_DESKTOP_BACKGROUND_DESKTOP_BACKGROUND_CONTROLLER_H_