[cc] Fix CompositorFrameSinkSupport BeginFrameAck interface.

services/ui/ws/display_client_compositor_frame_sink.cc

 // Copyright 2017 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 "services/ui/ws/display_client_compositor_frame_sink.h"
 
 #include "base/threading/thread_checker.h"
 #include "cc/output/compositor_frame_sink_client.h"
 
 namespace ui {
@@ skipping 30 matching lines @@
   begin_frame_source_.reset();
   cc::CompositorFrameSink::DetachFromClient();
 }
 
 void DisplayClientCompositorFrameSink::SubmitCompositorFrame(
     cc::CompositorFrame frame) {
   DCHECK(thread_checker_->CalledOnValidThread());
   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();
 
   if (!local_surface_id_.is_valid() ||
       frame_size != last_submitted_frame_size_) {
     local_surface_id_ = id_allocator_.GenerateId();
     display_private_->ResizeDisplay(frame_size);
   }
   display_private_->SetLocalSurfaceId(local_surface_id_,
@@ skipping 31 matching lines @@
 }
 
 void DisplayClientCompositorFrameSink::OnNeedsBeginFrames(
     bool needs_begin_frames) {
   DCHECK(thread_checker_->CalledOnValidThread());
   compositor_frame_sink_->SetNeedsBeginFrame(needs_begin_frames);
 }
 
 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
 }  // namespace ui