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

components/viz/frame_sinks/gpu_compositor_frame_sink.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/viz/frame_sinks/gpu_compositor_frame_sink.h"
 
 namespace viz {
 
 GpuCompositorFrameSink::GpuCompositorFrameSink(
     GpuCompositorFrameSinkDelegate* delegate,
@@ skipping 53 matching lines @@
 void GpuCompositorFrameSink::ClaimTemporaryReference(
     const cc::SurfaceId& surface_id) {
   support_->ClaimTemporaryReference(surface_id);
 }
 
 void GpuCompositorFrameSink::RequestCopyOfSurface(
     std::unique_ptr<cc::CopyOutputRequest> request) {
   support_->RequestCopyOfSurface(std::move(request));
 }
 
+void GpuCompositorFrameSink::RequestBeginFrames(
+    cc::mojom::FrameSinkObserverPtr observer) {
+  observer_ = std::move(observer);
+}
+
 void GpuCompositorFrameSink::OnBeginFrame(const cc::BeginFrameArgs& args) {
   if (client_)
     client_->OnBeginFrame(args);
+  if (observer_.is_bound())
+    observer_->OnBeginFrame();
 }
 
 void GpuCompositorFrameSink::ReclaimResources(
     const cc::ReturnedResourceArray& resources) {
   if (client_)
     client_->ReclaimResources(resources);
 }
 
 void GpuCompositorFrameSink::WillDrawSurface(
     const cc::LocalSurfaceId& local_surface_id,
     const gfx::Rect& damage_rect) {}
 
 void GpuCompositorFrameSink::OnClientConnectionLost() {
   client_connection_lost_ = true;
   // Request destruction of |this| only if both connections are lost.
   delegate_->OnClientConnectionLost(support_->frame_sink_id(),
                                     private_connection_lost_);
 }
 
 void GpuCompositorFrameSink::OnPrivateConnectionLost() {
   private_connection_lost_ = true;
   // Request destruction of |this| only if both connections are lost.
   delegate_->OnPrivateConnectionLost(support_->frame_sink_id(),
                                      client_connection_lost_);
 }
 
 }  // namespace viz