Merge 150885 - Reland " Preload default wallpaper."

ash/desktop_background/desktop_background_controller.h

Index: ash/desktop_background/desktop_background_controller.h
===================================================================
--- ash/desktop_background/desktop_background_controller.h	(revision 151025)
+++ ash/desktop_background/desktop_background_controller.h	(working copy)
@@ -76,6 +76,11 @@
   // Initialize root window's background.
   void OnRootWindowAdded(aura::RootWindow* root_window);
 
+  // Loads default wallpaper at |index| asynchronously but does not set the
+  // loaded image to current wallpaper. Resource bundle will cache the loaded
+  // image.
+  void CacheDefaultWallpaper(int index);
+
   // Loads default wallpaper at |index| asynchronously and sets to current
   // wallpaper after loaded. When |force_reload| is true, reload wallpaper
   // for all root windows even if |index| is the same as current wallpaper. It
@@ -145,6 +150,9 @@
   // Returns id for background container for unlocked and locked states.
   int GetBackgroundContainerId(bool locked);
 
+  // Returns the appropriate wallpaper resolution for all root windows.
+  WallpaperResolution GetAppropriateResolution();
+
   // Can change at runtime.
   bool locked_;