Fix login visual hitch on chromebook

chrome/browser/chromeos/login/wallpaper_manager.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_LOGIN_WALLPAPER_MANAGER_H_
 #define CHROME_BROWSER_CHROMEOS_LOGIN_WALLPAPER_MANAGER_H_
 
 #include <string>
 
 #include "ash/desktop_background/desktop_background_controller.h"
@@ skipping 45 matching lines @@
 
 // This class maintains wallpapers for users who have logged into this Chrome
 // OS device.
 class WallpaperManager: public system::TimezoneSettings::Observer,
                         public chromeos::PowerManagerClient::Observer,
                         public content::NotificationObserver {
  public:
   static WallpaperManager* Get();
 
   WallpaperManager();
+  virtual ~WallpaperManager();
+
+  // Indicates imminent shutdown, allowing the WallpaperManager to remove any
+  // observers it has registered.
+  void Shutdown();
 
   // Registers wallpaper manager preferences.
   static void RegisterPrefs(PrefServiceSimple* local_state);
 
-  // Adds PowerManagerClient and TimeZoneSettings observers. It needs to be
-  // added after PowerManagerClient has been initialized.
-  void AddObservers();
-
   // Loads wallpaper asynchronously if the current wallpaper is not the
   // wallpaper of logged in user.
   void EnsureLoggedInUserWallpaperLoaded();
 
   // Clears ONLINE and CUSTOM wallpaper cache.
   void ClearWallpaperCache();
 
   // Gets encoded wallpaper from cache. Returns true if success.
   bool GetWallpaperFromCache(const std::string& email,
                              gfx::ImageSkia* wallpaper);
@@ skipping 67 matching lines @@
                                  ash::WallpaperLayout layout);
 
   // Updates current wallpaper. It may switch the size of wallpaper based on the
   // current display's resolution.
   void UpdateWallpaper();
 
  private:
   friend class WallpaperManagerBrowserTest;
   typedef std::map<std::string, gfx::ImageSkia> CustomWallpaperMap;
 
-  virtual ~WallpaperManager();
-
   // The number of wallpapers have loaded. For test only.
   int loaded_wallpapers() const { return loaded_wallpapers_; }
 
   // Change the wallpapers for users who choose DAILY wallpaper type. Updates
   // current wallpaper if it changed. This function should be called at exactly
   // at 0am if chromeos device is on.
   void BatchUpdateWallpaper();
 
   // Cache some (or all) logged in users' wallpapers to memory at login
   // screen. It should not compete with first wallpaper loading when boot
@@ skipping 125 matching lines @@
   content::NotificationRegistrar registrar_;
 
   base::OneShotTimer<WallpaperManager> timer_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperManager);
 };
 
 }  // namespace chromeos
 
 #endif  // CHROME_BROWSER_CHROMEOS_LOGIN_WALLPAPER_MANAGER_H_