cc: Devirtualize DisplayItem::ExternalMemoryUsage().

cc/playback/drawing_display_item.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_PLAYBACK_DRAWING_DISPLAY_ITEM_H_
 #define CC_PLAYBACK_DRAWING_DISPLAY_ITEM_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 19 matching lines @@
                               std::vector<uint32_t>* used_engine_picture_ids);
   explicit DrawingDisplayItem(const DrawingDisplayItem& item);
   ~DrawingDisplayItem() override;
 
   void ToProtobuf(proto::DisplayItem* proto) const override;
   sk_sp<const SkPicture> GetPicture() const override;
   void Raster(SkCanvas* canvas,
               SkPicture::AbortCallback* callback) const override;
   void AsValueInto(const gfx::Rect& visual_rect,
                    base::trace_event::TracedValue* array) const override;
-  size_t ExternalMemoryUsage() const override;
 
+  size_t ExternalMemoryUsage() const;
   int ApproximateOpCount() const;
 
   void CloneTo(DrawingDisplayItem* item) const;
 
  private:
   void SetNew(sk_sp<const SkPicture> picture);
 
   sk_sp<const SkPicture> picture_;
 };
 
 }  // namespace cc
 
 #endif  // CC_PLAYBACK_DRAWING_DISPLAY_ITEM_H_