[cc] Fix CompositorFrameSinkSupport BeginFrameAck interface.

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 57 matching lines @@
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // cc::ExternalBeginFrameSourceClient 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_.
+  // If there was damage, the submitted CompositorFrame includes the ack.
+  if (!ack.has_damage)
+    frame_sink_->BeginFrameDidNotSwap(ack);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // SurfaceObserver overrides:
 
 void CompositorFrameSinkHolder::OnSurfaceDestroying(Surface* surface) {
   surface_->RemoveSurfaceObserver(this);
   surface_ = nullptr;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // ExoComopositorFrameSink, private:
 
 CompositorFrameSinkHolder::~CompositorFrameSinkHolder() {
   if (surface_)
     surface_->RemoveSurfaceObserver(this);
 }
 
 }  // namespace exo