[cc] Track observer status in ExternalBeginFrameSource.

content/renderer/gpu/compositor_external_begin_frame_source.cc

 // Copyright 2014 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/compositor_external_begin_frame_source.h"
 
 #include "content/common/view_messages.h"
 #include "ipc/ipc_sync_channel.h"
 #include "ipc/ipc_sync_message_filter.h"
 
@@ skipping 46 matching lines @@
 
 bool CompositorExternalBeginFrameSource::IsThrottled() const {
   return true;
 }
 
 void CompositorExternalBeginFrameSource::OnNeedsBeginFrames(
     bool needs_begin_frames) {
   Send(new ViewHostMsg_SetNeedsBeginFrames(routing_id_, needs_begin_frames));
 }
 
+void CompositorExternalBeginFrameSource::OnDidFinishFrame(
+    const cc::BeginFrameAck& ack) {
+  // TODO(eseckler): Pass on the ack to the view host.
+}
+
 void CompositorExternalBeginFrameSource::OnMessageReceived(
     const IPC::Message& message) {
   DCHECK(CalledOnValidThread());
   DCHECK(begin_frame_source_proxy_);
   IPC_BEGIN_MESSAGE_MAP(CompositorExternalBeginFrameSource, message)
     IPC_MESSAGE_HANDLER(ViewMsg_SetBeginFramePaused,
                         OnSetBeginFrameSourcePaused)
     IPC_MESSAGE_HANDLER(ViewMsg_BeginFrame, OnBeginFrame)
   IPC_END_MESSAGE_MAP()
 }
 
 void CompositorExternalBeginFrameSource::OnSetBeginFrameSourcePaused(
     bool paused) {
   external_begin_frame_source_.OnSetBeginFrameSourcePaused(paused);
 }
 
 void CompositorExternalBeginFrameSource::OnBeginFrame(
     const cc::BeginFrameArgs& args) {
   external_begin_frame_source_.OnBeginFrame(args);
 }
 
 bool CompositorExternalBeginFrameSource::Send(IPC::Message* message) {
   return message_sender_->Send(message);
 }
 
 }  // namespace content