mus: Embedder can request and observe BeginFrame for embedded client.

components/viz/frame_sinks/gpu_root_compositor_frame_sink.cc

Index: components/viz/frame_sinks/gpu_root_compositor_frame_sink.cc
diff --git a/components/viz/frame_sinks/gpu_root_compositor_frame_sink.cc b/components/viz/frame_sinks/gpu_root_compositor_frame_sink.cc
index b614fe8811b7dff661545abf62c54a390754023e..0beeab6c052bc140363f211883f39255508bb007 100644
--- a/components/viz/frame_sinks/gpu_root_compositor_frame_sink.cc
+++ b/components/viz/frame_sinks/gpu_root_compositor_frame_sink.cc
@@ -104,6 +104,11 @@ void GpuRootCompositorFrameSink::RequestCopyOfSurface(
   support_->RequestCopyOfSurface(std::move(request));
 }
 
+void GpuRootCompositorFrameSink::RequestBeginFrame(
+    cc::mojom::FrameSinkObserverPtr observer) {
+  NOTREACHED() << "Stahp";

[Fady Samuel, 2017/05/12 22:42:55]

Better message?

[sadrul, 2017/05/13 03:01:38]

Sorry, meant to cleanup. Removed the message here, and instead added comment
explaining why NOTREACHED()

+}
+
 void GpuRootCompositorFrameSink::DisplayOutputSurfaceLost() {
   // TODO(staraz): Implement this. Client should hear about context/output
   // surface lost.