cc: Devirtualize DisplayItem::ExternalMemoryUsage().

cc/playback/display_item.h

Index: cc/playback/display_item.h
diff --git a/cc/playback/display_item.h b/cc/playback/display_item.h
index 08d3d0116347027ca8158e250615cd94f5c2db6f..4e74e9079e76e9f9da7c3400aba25af25a49ff99 100644
--- a/cc/playback/display_item.h
+++ b/cc/playback/display_item.h
@@ -24,6 +24,22 @@ class DisplayItem;
 
 class CC_EXPORT DisplayItem {
  public:
+  enum Type {
+    CLIP,
+    END_CLIP,
+    CLIP_PATH,
+    END_CLIP_PATH,
+    COMPOSITING,
+    END_COMPOSITING,
+    DRAWING,
+    FILTER,
+    END_FILTER,
+    FLOAT_CLIP,
+    END_FLOAT_CLIP,
+    TRANSFORM,
+    END_TRANSFORM,
+  };
+
   virtual ~DisplayItem() {}
 
   virtual void ToProtobuf(proto::DisplayItem* proto) const = 0;
@@ -32,11 +48,13 @@ class CC_EXPORT DisplayItem {
                       SkPicture::AbortCallback* callback) const = 0;
   virtual void AsValueInto(const gfx::Rect& visual_rect,
                            base::trace_event::TracedValue* array) const = 0;
-  // For tracing.
-  virtual size_t ExternalMemoryUsage() const = 0;
+
+  Type type() const { return type_; }
 
  protected:
-  DisplayItem();
+  explicit DisplayItem(Type type) : type_(type) {}
+
+  const Type type_;
 };
 
 }  // namespace cc