Asynchronously load wallpapers when user pod is selected.

chrome/browser/chromeos/background/desktop_background_observer.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 CHROME_BROWSER_CHROMEOS_BACKGROUND_DESKTOP_BACKGROUND_OBSERVER_H_
-#define CHROME_BROWSER_CHROMEOS_BACKGROUND_DESKTOP_BACKGROUND_OBSERVER_H_
-#pragma once
-
-#include "content/public/browser/notification_observer.h"
-#include "content/public/browser/notification_registrar.h"
-
-namespace ash {
-class UserWallpaperDelegate;
-}
-
-namespace chromeos {
-
-ash::UserWallpaperDelegate* CreateUserWallpaperDelegate();
-
-// Listens for background change events and passes them to the Aura shell's
-// DesktopBackgroundController class.
-class DesktopBackgroundObserver : public content::NotificationObserver {
- public:
-  DesktopBackgroundObserver();
-  virtual ~DesktopBackgroundObserver();
-
- private:
-
-  // content::NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
-
-  content::NotificationRegistrar registrar_;
-
-  DISALLOW_COPY_AND_ASSIGN(DesktopBackgroundObserver);
-};
-
-}  // namespace chromeos
-#endif  // CHROME_BROWSER_CHROMEOS_BACKGROUND_DESKTOP_BACKGROUND_OBSERVER_H_