ShowWallpaperAnimationObserver 23 ash/desktop_background/desktop_background_widget_controller.cc ShowWallpaperAnimationObserver(RootWindowController* root_window_controller, ShowWallpaperAnimationObserver 64 ash/desktop_background/desktop_background_widget_controller.cc DISALLOW_COPY_AND_ASSIGN(ShowWallpaperAnimationObserver); ShowWallpaperAnimationObserver 111 ash/desktop_background/desktop_background_widget_controller.cc settings.AddObserver(new ShowWallpaperAnimationObserver(