[cc] Fix CompositorFrameSinkSupport BeginFrameAck interface.

services/ui/ws/display_client_compositor_frame_sink.cc

Index: services/ui/ws/display_client_compositor_frame_sink.cc
diff --git a/services/ui/ws/display_client_compositor_frame_sink.cc b/services/ui/ws/display_client_compositor_frame_sink.cc
index 5d719fa1dab4290c2bcdd7c33ffca4ff8adfccf4..01c16fc804b90d1ce25db1f32c6ebec8e6283da3 100644
--- a/services/ui/ws/display_client_compositor_frame_sink.cc
+++ b/services/ui/ws/display_client_compositor_frame_sink.cc
@@ -48,6 +48,9 @@ void DisplayClientCompositorFrameSink::SubmitCompositorFrame(
   if (!compositor_frame_sink_)
     return;
 
+  DCHECK_LE(cc::BeginFrameArgs::kStartingFrameNumber,
+            frame.metadata.begin_frame_ack.sequence_number);
+
   gfx::Size frame_size = last_submitted_frame_size_;
   if (!frame.render_pass_list.empty())
     frame_size = frame.render_pass_list.back()->output_rect.size();
@@ -99,7 +102,9 @@ void DisplayClientCompositorFrameSink::OnNeedsBeginFrames(
 
 void DisplayClientCompositorFrameSink::OnDidFinishFrame(
     const cc::BeginFrameAck& ack) {
-  // TODO(eseckler): Pass on the ack to compositor_frame_sink_.
+  // If there was damage, the submitted CompositorFrame includes the ack.
+  if (!ack.has_damage)
+    compositor_frame_sink_->BeginFrameDidNotSwap(ack);
 }
 
 }  // namespace ws