Load 2x resources on demand

ui/app_list/app_list_item_view.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/app_list/app_list_item_view.h"
 
 #include <algorithm>
 
 #include "base/bind.h"
 #include "base/message_loop.h"
@@ skipping 86 matching lines @@
   }
 
   void ResizeAndGenerateShadow() {
     if (cancel_flag_.IsSet())
       return;
 
     gfx::ImageSkia resized(gfx::ImageSkiaOperations::CreateResizedImage(image_,
         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() {
     cancel_flag_.Set();
   }
 
   const gfx::ImageSkia& image() const {
     return image_;
   }
 
@@ skipping 181 matching lines @@
     apps_grid_view_->SetSelectedItem(this);
     title_->SetEnabledColor(kTitleHoverColor);
   } else {
     apps_grid_view_->ClearSelectedItem(this);
     model_->SetHighlighted(false);
     title_->SetEnabledColor(kTitleColor);
   }
 }
 
 }  // namespace app_list