cc: Devirtualize DisplayItem::ExternalMemoryUsage().

cc/playback/transform_display_item.h

Index: cc/playback/transform_display_item.h
diff --git a/cc/playback/transform_display_item.h b/cc/playback/transform_display_item.h
index 15ec94bd7172fd766d078c18a26daa8dda74a364..728fe9df70a20d97fe5d4d0a5cf676d9c24f5038 100644
--- a/cc/playback/transform_display_item.h
+++ b/cc/playback/transform_display_item.h
@@ -29,8 +29,8 @@ class CC_EXPORT TransformDisplayItem : public DisplayItem {
               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:
@@ -54,7 +54,6 @@ class CC_EXPORT EndTransformDisplayItem : public DisplayItem {
               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; }
 };