cc: Add image decode control in the compositor.

cc/playback/display_item_list.cc

 // Copyright 2014 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 "cc/playback/display_item_list.h"
 
 #include <stddef.h>
 
 #include <string>
 
@@ skipping 291 matching lines @@
     float raster_scale,
     std::vector<DrawImage>* images) {
   image_map_.GetDiscardableImagesInRect(rect, raster_scale, images);
 }
 
 bool DisplayItemList::HasDiscardableImageInRect(
     const gfx::Rect& layer_rect) const {
   return image_map_.HasDiscardableImageInRect(layer_rect);
 }
 
+bool DisplayItemList::MayHaveDiscardableImages() const {
+  return !image_map_.empty();
+}
+
 }  // namespace cc