cc: Devirtualize DisplayItem::ExternalMemoryUsage().

cc/playback/transform_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_TRANSFORM_DISPLAY_ITEM_H_
 #define CC_PLAYBACK_TRANSFORM_DISPLAY_ITEM_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 11 matching lines @@
  public:
   explicit TransformDisplayItem(const gfx::Transform& transform);
   explicit TransformDisplayItem(const proto::DisplayItem& proto);
   ~TransformDisplayItem() override;
 
   void ToProtobuf(proto::DisplayItem* proto) 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 { return 0; }
   int ApproximateOpCount() const { return 1; }
 
  private:
   void SetNew(const gfx::Transform& transform);
 
   gfx::Transform transform_;
 };
 
 class CC_EXPORT EndTransformDisplayItem : public DisplayItem {
  public:
   EndTransformDisplayItem();
   explicit EndTransformDisplayItem(const proto::DisplayItem& proto);
   ~EndTransformDisplayItem() override;
 
   static std::unique_ptr<EndTransformDisplayItem> Create() {
     return base::MakeUnique<EndTransformDisplayItem>();
   }
 
   void ToProtobuf(proto::DisplayItem* proto) 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;
 
   int ApproximateOpCount() const { return 0; }
 };
 
 }  // namespace cc
 
 #endif  // CC_PLAYBACK_TRANSFORM_DISPLAY_ITEM_H_