Implement DisplayList GatherPixelRefs

cc/resources/display_item_list.h

 // 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.
 
 #ifndef CC_RESOURCES_DISPLAY_ITEM_LIST_H_
 #define CC_RESOURCES_DISPLAY_ITEM_LIST_H_
 
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/trace_event/trace_event.h"
 #include "cc/base/cc_export.h"
 #include "cc/base/scoped_ptr_vector.h"
 #include "cc/resources/display_item.h"
+#include "cc/resources/pixel_ref_map.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkPicture.h"
 #include "ui/gfx/geometry/rect.h"
 
 class SkCanvas;
 class SkDrawPictureCallback;
 
 namespace cc {
 
 class CC_EXPORT DisplayItemList
@@ skipping 13 matching lines @@
   void CreateAndCacheSkPicture();
 
   bool IsSuitableForGpuRasterization() const;
   int ApproximateOpCount() const;
   size_t PictureMemoryUsage() const;
 
   scoped_refptr<base::trace_event::ConvertableToTraceFormat> AsValue() const;
 
   void EmitTraceSnapshot() const;
 
+  void GatherPixelRefs(const gfx::Size& grid_cell_size);
+
  private:
   DisplayItemList();
   ~DisplayItemList();
   ScopedPtrVector<DisplayItem> items_;
   skia::RefPtr<SkPicture> picture_;
 
   gfx::Rect layer_rect_;
   bool is_suitable_for_gpu_rasterization_;
   int approximate_op_count_;
 
+  scoped_ptr<PixelRefMap> pixel_refs_;
+
   friend class base::RefCountedThreadSafe<DisplayItemList>;
+  friend class PixelRefMap::Iterator;
   DISALLOW_COPY_AND_ASSIGN(DisplayItemList);
 };
 
 }  // namespace cc
 
 #endif  // CC_RESOURCES_DISPLAY_ITEM_LIST_H_