cc: Introduce BeginFrame sequence numbers and acknowledgements.

content/renderer/android/synchronous_compositor_frame_sink.cc

 // Copyright 2013 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 "content/renderer/android/synchronous_compositor_frame_sink.h"
 
 #include <vector>
 
 #include "base/auto_reset.h"
 #include "base/location.h"
@@ skipping 453 matching lines @@
 }
 
 void SynchronousCompositorFrameSink::ReturnResources(
     const cc::ReturnedResourceArray& resources) {
   DCHECK(resources.empty());
   client_->ReclaimResources(resources);
 }
 
 void SynchronousCompositorFrameSink::SetBeginFrameSource(
     cc::BeginFrameSource* begin_frame_source) {
-  // Software output is synchronous and doesn't use a BeginFrameSource.
-  NOTREACHED();
+  // Software output is synchronous and doesn't use the frame sink's (Display's)
+  // BeginFrameSource.
 }
 
 }  // namespace content