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

services/ui/ws/server_window_compositor_frame_sink_manager.cc

Index: services/ui/ws/server_window_compositor_frame_sink_manager.cc
diff --git a/services/ui/ws/server_window_compositor_frame_sink_manager.cc b/services/ui/ws/server_window_compositor_frame_sink_manager.cc
index 94ab45b5303db9ef9558576bd214219a9f40dffc..ae7244e4f51119a1772632ff31f177bd83bb6868 100644
--- a/services/ui/ws/server_window_compositor_frame_sink_manager.cc
+++ b/services/ui/ws/server_window_compositor_frame_sink_manager.cc
@@ -63,5 +63,10 @@ void ServerWindowCompositorFrameSinkManager::ClaimTemporaryReference(
   compositor_frame_sink_->ClaimTemporaryReference(surface_id);
 }
 
+void ServerWindowCompositorFrameSinkManager::RequestBeginFrame(
+    cc::mojom::FrameSinkObserverPtr observer) {

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

if (!compositor_frame_sink_.is_bound()) {
  pending_compositor_frame_sink_request_ =
     mojo::MakeRequest(&compositor_frame_sink_);
}

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

Done.

+  compositor_frame_sink_->RequestBeginFrame(std::move(observer));
+}
+
 }  // namespace ws
 }  // namespace ui