Asynchronously load wallpapers when user pod is selected.

ash/desktop_background/desktop_background_resources.cc

Index: ash/desktop_background/desktop_background_resources.cc
diff --git a/ash/desktop_background/desktop_background_resources.cc b/ash/desktop_background/desktop_background_resources.cc
index f53ac63fc4837c32b2c47b4cc9ccc68a2fb94906..a9fc8dcdbf97e034a36686652a2ef16527918073 100644
--- a/ash/desktop_background/desktop_background_resources.cc
+++ b/ash/desktop_background/desktop_background_resources.cc
@@ -257,13 +257,8 @@ int GetWallpaperCount() {
   return kDefaultWallpaperCount;
 }
 
-const SkBitmap& GetWallpaper(int index) {
-  DCHECK(index >= 0 && index < kDefaultWallpaperCount);
-  return *ui::ResourceBundle::GetSharedInstance().GetImageNamed(
-      kDefaultWallpapers[index].id).ToSkBitmap();
-}
-
 const WallpaperInfo& GetWallpaperInfo(int index) {
+  DCHECK(index >= 0 && index < kDefaultWallpaperCount);
   return kDefaultWallpapers[index];
 }