Load 2x resources on demand

ui/app_list/app_list_item_view.cc

Index: ui/app_list/app_list_item_view.cc
diff --git a/ui/app_list/app_list_item_view.cc b/ui/app_list/app_list_item_view.cc
index 8c405fbe26fcb1f3a55ea54bc63ef1e22c5260bb..a68dff0d6b9f182c8871a5c463cbf90bf6b6d17d 100644
--- a/ui/app_list/app_list_item_view.cc
+++ b/ui/app_list/app_list_item_view.cc
@@ -104,16 +104,12 @@ class AppListItemView::IconOperation
         skia::ImageOperations::RESIZE_BEST, size_));
     gfx::ImageSkia shadow(
         gfx::ImageSkiaOperations::CreateImageWithDropShadow(resized, shadows_));
-
-    // The following statement causes shadowed image being generated for all
-    // existing image reps in |image_|. This is needed so that expensive shadow
-    // generation does not run on UI thread.
-    gfx::ImageSkia::ImageSkiaReps image_reps = image_.image_reps();
-    for (gfx::ImageSkia::ImageSkiaReps::const_iterator it = image_reps.begin();
-         it != image_reps.end(); ++it) {
-      shadow.GetRepresentation(it->scale_factor());
-    }
     image_ = shadow;
+    // Make sure that the image contains ImageSkiaReps for supported
+    // scale factors.
+    image_.EnsureRepsForSupportedScaleFactors();
+    // All images are generated. We no longer need source.
+    image_.DeleteSource();
   }
 
   void Cancel() {