[cc] Track observer status in ExternalBeginFrameSource.

components/exo/compositor_frame_sink_holder.cc

 // Copyright 2016 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/exo/compositor_frame_sink_holder.h"
 
 #include "cc/resources/returned_resource.h"
 #include "components/exo/surface.h"
 
 namespace exo {
@@ skipping 40 matching lines @@
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // cc::mojom::MojoCompositorFrameSinkClient overrides:
 
 void CompositorFrameSinkHolder::DidReceiveCompositorFrameAck() {
   // TODO(staraz): Implement this
 }
 
 void CompositorFrameSinkHolder::OnBeginFrame(const cc::BeginFrameArgs& args) {
+  // TODO(eseckler): Hook up exo::Surface to the ExternalBFS.
   if (surface_)
     surface_->BeginFrame(args.frame_time);
 
   begin_frame_source_->OnBeginFrame(args);
 }
 
 void CompositorFrameSinkHolder::ReclaimResources(
     const cc::ReturnedResourceArray& resources) {
   for (auto& resource : resources) {
     auto it = release_callbacks_.find(resource.id);
@@ skipping 22 matching lines @@
 
 void CompositorFrameSinkHolder::OnBeginFrameSourcePausedChanged(bool paused) {}
 
 ////////////////////////////////////////////////////////////////////////////////
 // cc::ExternalBeginFrameSouceClient overrides:
 
 void CompositorFrameSinkHolder::OnNeedsBeginFrames(bool needs_begin_frames) {
   frame_sink_->SetNeedsBeginFrame(needs_begin_frames);
 }
 
+void CompositorFrameSinkHolder::OnDidFinishFrame(const cc::BeginFrameAck& ack) {
+  // TODO(eseckler): Pass on the ack to frame_sink_.
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // SurfaceObserver overrides:
 
 void CompositorFrameSinkHolder::OnSurfaceDestroying(Surface* surface) {
   surface_->RemoveSurfaceObserver(this);
   surface_ = nullptr;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // ExoComopositorFrameSink, private:
 
 CompositorFrameSinkHolder::~CompositorFrameSinkHolder() {
   if (surface_)
     surface_->RemoveSurfaceObserver(this);
 }
 
 void CompositorFrameSinkHolder::UpdateNeedsBeginFrame() {
   if (!begin_frame_source_)
     return;
 
   bool needs_begin_frame = surface_ && surface_->NeedsBeginFrame();
   if (needs_begin_frame == needs_begin_frame_)
     return;
 
   needs_begin_frame_ = needs_begin_frame;
   OnNeedsBeginFrames(needs_begin_frame_);
 }
 
 }  // namespace exo