Merge 159822 - ash: Display system background while loading wallpaper.

ash/root_window_controller.h

Index: ash/root_window_controller.h
===================================================================
--- ash/root_window_controller.h	(revision 160653)
+++ ash/root_window_controller.h	(working copy)
@@ -27,6 +27,7 @@
 class EventClientImpl;
 class RootWindowLayoutManager;
 class ScreenDimmer;
+class SystemBackgroundController;
 class WorkspaceController;
 
 // This class maintains the per root window state for ash. This class
@@ -57,9 +58,16 @@
 
   aura::Window* GetContainer(int container_id);
 
+  void InitLayoutManagers();
   void CreateContainers();
-  void InitLayoutManagers();
 
+  // Initializes |background_|.  |is_first_run_after_boot| determines the
+  // background's initial color.
+  void CreateSystemBackground(bool is_first_run_after_boot);
+
+  // Updates |background_| to be black after the desktop background is visible.
+  void HandleDesktopBackgroundVisible();
+
   // Deletes associated objects and clears the state, but doesn't delete
   // the root window yet. This is used to delete a secondary displays'
   // root window safely when the display disconnect signal is received,
@@ -83,6 +91,12 @@
   scoped_ptr<aura::RootWindow> root_window_;
   internal::RootWindowLayoutManager* root_window_layout_;
 
+  // A background layer that's displayed beneath all other layers.  Without
+  // this, portions of the root window that aren't covered by layers will be
+  // painted white; this can show up if e.g. it takes a long time to decode the
+  // desktop background image when displaying the login screen.
+  scoped_ptr<SystemBackgroundController> background_;
+
   // An event filter that pre-handles all key events to send them to an IME.
   scoped_ptr<internal::EventClientImpl> event_client_;
   scoped_ptr<internal::ScreenDimmer> screen_dimmer_;