Make OffscreenCanvas animation in sync with its placeholder canvas's parent frame rate

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 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/gpu/render_widget_compositor.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <limits>
@@ skipping 1100 matching lines @@
   proto.SerializeToArray(serialized.data(), signed_size);
   delegate_->ForwardCompositorProto(serialized);
 }
 
 void RenderWidgetCompositor::SetFrameSinkId(
     const cc::FrameSinkId& frame_sink_id) {
   frame_sink_id_ = frame_sink_id;
   layer_tree_host_->SetFrameSinkId(frame_sink_id);
 }
 
+cc::FrameSinkId RenderWidgetCompositor::getFrameSinkId() {
+  return frame_sink_id_;

[dcheng, 2017/01/20 08:44:12]

Nit: function definitions should be ordered by order of declaration:
https://chromium.googlesource.com/chromium/src/+/master/styleguide/c++/c++.md...

[xlai (Olivia), 2017/01/20 16:36:21]

Done.

+}
+
 void RenderWidgetCompositor::OnHandleCompositorProto(
     const std::vector<uint8_t>& proto) {
   DCHECK(remote_proto_channel_receiver_);
 
   std::unique_ptr<cc::proto::CompositorMessage> deserialized(
       new cc::proto::CompositorMessage);
   int signed_size = base::checked_cast<int>(proto.size());
   if (!deserialized->ParseFromArray(proto.data(), signed_size)) {
     LOG(ERROR) << "Unable to parse compositor proto.";
     return;
   }
 
   remote_proto_channel_receiver_->OnProtoReceived(std::move(deserialized));
 }
 
 void RenderWidgetCompositor::SetPaintedDeviceScaleFactor(
     float device_scale) {
   layer_tree_host_->GetLayerTree()->SetPaintedDeviceScaleFactor(device_scale);
 }
 
 void RenderWidgetCompositor::SetDeviceColorSpace(
     const gfx::ColorSpace& color_space) {
   layer_tree_host_->GetLayerTree()->SetDeviceColorSpace(color_space);
 }
 
 }  // namespace content