Add support for Ash to Notifications

chrome/browser/chromeos/login/user_manager_impl.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 "chrome/browser/chromeos/login/user_manager_impl.h"
 
 #include <vector>
 
 #include "ash/shell.h"
 #include "ash/desktop_background/desktop_background_controller.h"
@@ skipping 391 matching lines @@
       // In customized mode, we use index pref to save the user selected
       // wallpaper layout. See function SaveWallpaperToLocalState().
       ash::WallpaperLayout layout = static_cast<ash::WallpaperLayout>(index);
       // Load user image asynchronously.
       image_loader_->Start(
           wallpaper_path, 0, false,
           base::Bind(&UserManagerImpl::OnCustomWallpaperLoaded,
                      base::Unretained(this), email, layout));
       return;
     }
+    if (!ash::Shell::HasInstance())
+      return;
     ash::Shell::GetInstance()->desktop_background_controller()->
         SetDefaultWallpaper(index);
   }
 }
 
 void UserManagerImpl::SessionStarted() {
   session_started_ = true;
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_SESSION_STARTED,
       content::NotificationService::AllSources(),
@@ skipping 1130 matching lines @@
     BrowserThread::PostTask(
         BrowserThread::FILE,
         FROM_HERE,
         base::Bind(&UserManagerImpl::DeleteUserImage,
                    base::Unretained(this),
                    image_path));
   }
 }
 
 }  // namespace chromeos