Always use the WebFrameWidget when attaching the root graphics

third_party/WebKit/public/web/WebFrameWidget.h

Index: third_party/WebKit/public/web/WebFrameWidget.h
diff --git a/third_party/WebKit/public/web/WebFrameWidget.h b/third_party/WebKit/public/web/WebFrameWidget.h
index d856c943f88e1c4a7d22b767b74269065fbd79e4..dbae7ca4eaca0d30c5cfef94da18e84be897a87d 100644
--- a/third_party/WebKit/public/web/WebFrameWidget.h
+++ b/third_party/WebKit/public/web/WebFrameWidget.h
@@ -37,7 +37,9 @@
 
 namespace blink {
 
+class CompositorAnimationTimeline;
 class CompositorProxyClient;
+class GraphicsLayer;
 class WebLocalFrame;
 class WebView;
 class WebWidgetClient;
@@ -79,6 +81,9 @@ public:
     virtual void scheduleAnimation() = 0;
     virtual CompositorProxyClient* createCompositorProxyClient() = 0;
     virtual WebWidgetClient* client() const = 0;
+    virtual void setRootGraphicsLayer(GraphicsLayer*) = 0;

[dcheng, 2016/07/04 07:34:36]

Hmm, can we move the Blink-internal methods to their own section with a comment?
I'll clean it up in a followup CL.

[lfg, 2016/07/04 17:46:13]

Done.

+    virtual void attachCompositorAnimationTimeline(CompositorAnimationTimeline*) = 0;
+    virtual void detachCompositorAnimationTimeline(CompositorAnimationTimeline*) = 0;
 };
 
 } // namespace blink