Fix white flash when user sings out and wallpaper animation regression

ash/desktop_background/desktop_background_controller.h

Index: ash/desktop_background/desktop_background_controller.h
diff --git a/ash/desktop_background/desktop_background_controller.h b/ash/desktop_background/desktop_background_controller.h
index edcd803a2f28e923301e6f9e8ecced9e8feda304..37b37895ba915d63085880bf15319dc5088722dd 100644
--- a/ash/desktop_background/desktop_background_controller.h
+++ b/ash/desktop_background/desktop_background_controller.h
@@ -24,6 +24,10 @@ class RootWindow;
 
 namespace ash {
 
+namespace internal {
+class DesktopBackgroundWidgetController;
+}
+
 class UserWallpaperDelegate {
  public:
   virtual ~UserWallpaperDelegate() {}
@@ -95,6 +99,9 @@ class ASH_EXPORT DesktopBackgroundController : public aura::WindowObserver {
   // Cancels the current wallpaper loading operation.
   void CancelPendingWallpaperOperation();
 
+  // Sets the current used component for |root_window|.
+  void SetComponentForRootWindow(aura::RootWindow* root_window);
+
   // Sets the desktop background to solid color mode and creates a solid
   // |color| layout.
   void SetDesktopBackgroundSolidColorMode(SkColor color);
@@ -160,6 +167,10 @@ class ASH_EXPORT DesktopBackgroundController : public aura::WindowObserver {
 
   SkColor background_color_;
 
+  typedef std::map<aura::RootWindow*,
+      internal::DesktopBackgroundWidgetController*> RootWindowComponentMap;
+  RootWindowComponentMap root_window_component_map_;

[sky, 2012/08/10 19:20:37]

You never clean this state as roots are removed. I think it would be better to
store this state as a property on the rootwindow.

[bshe, 2012/08/10 19:51:41]

This map is a place to store the component for root window. When animation
finished, the component is stored as a property (kWindowDesktopComponent) on the
root window. The reason I have to wait for the animation finish is because if we
set that property immediately, the old component is removed right away. And a
white screen will be displayed. The new wallpaper/component will fade in from
that white screen. So to avoid the white screen issue, I need to set the
property after animation finished. Given that we already have a property to save
the data, I just want to confirm with you that it is OK to create another
property (something like kWindowDesktopComponentTemp?) on root window to save
the component temporarily (before animation finished). I am not familiar with
root window property, so I am not sure if it is cheap enough. Thanks for
suggestion.

On 2012/08/10 19:20:37, sky wrote:

+
   // The current wallpaper.
   scoped_ptr<WallpaperData> current_wallpaper_;