Asynchronously load wallpapers when user pod is selected.

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"
 #include "base/basictypes.h"
+#include "base/memory/weak_ptr.h"
 
 class SkBitmap;
 
 namespace ash {
 
 class UserWallpaperDelegate {
  public:
   virtual ~UserWallpaperDelegate() {}
 
   // Gets the index of user selected wallpaper.
@@ skipping 17 matching lines @@
   };
 
   DesktopBackgroundController();
   virtual ~DesktopBackgroundController();
 
   // Get the desktop background mode.
   BackgroundMode desktop_background_mode() const {
     return desktop_background_mode_;
   }
 
-  // Sets the desktop background to image mode and create a new background
-  // widget with user selected wallpaper or default wallpaper. Delete the old
-  // widget if any.
-  void SetDesktopBackgroundImageMode();
+  // Load default wallpaper at |index| asynchronously and set to current
+  // wallpaper after loaded.
+  void SetDefaultWallpaper(int index);
+
+  // Cancel the current wallpaper loading operation.
+  void CancelPendingWallpaperOperation();
+
+  // Load logged in user wallpaper asynchronously and set to current wallpaper
+  // after loaded.
+  void SetLoggedInUserWallpaper();
 
   // Sets the desktop background to solid color mode and create a solid color
   // layout.
   void SetDesktopBackgroundSolidColorMode();
 
  private:
+  // An operation to asynchronously load wallpaper.
+  class WallpaperOperation;
+
+  // Sets the desktop background to image mode and create a new background
+  // widget with user selected wallpaper or default wallpaper. Delete the old
+  // widget if any.
+  void SetDesktopBackgroundImageMode(scoped_refptr<WallpaperOperation> wo);
+
+  // Default wallpapper loaded, set the background mode to image mode.
+  void OnWallpaperLoadCompleted(scoped_refptr<WallpaperOperation> wo);
+
+  // Create an empty wallpaper. Some tests require a wallpaper widget is ready
+  // when running. However, the wallpaper widgets are now created asynchronously
+  // . If loading a real wallpaper, there are cases that these tests crash
+  // because the required widget is not ready. This function synchronously
+  // creates an empty widget for those tests to prevent crashes. An example test
+  // is SystemGestureEventFilterTest.ThreeFingerSwipe.
+  void CreateEmptyWallpaper();
+
   // 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_