Implement video frame acknowledgements in the chromoting protocol.

remoting/host/client_session.cc

Index: remoting/host/client_session.cc
diff --git a/remoting/host/client_session.cc b/remoting/host/client_session.cc
index ef6f5a6a4c7bb03645fc4a2197f389f85a294d5d..905539bc8f5fb690298a0d8af4abba7554537cac 100644
--- a/remoting/host/client_session.cc
+++ b/remoting/host/client_session.cc
@@ -447,6 +447,7 @@ void ClientSession::ResetVideoPipeline() {
   DCHECK(CalledOnValidThread());
 
   mouse_shape_pump_.reset();
+  connection_->set_video_feedback_stub(nullptr);
   video_frame_pump_.reset();
 
   // Create VideoEncoder and DesktopCapturer to match the session's video
@@ -484,6 +485,9 @@ void ClientSession::ResetVideoPipeline() {
 
   // Pause capturing if necessary.
   video_frame_pump_->Pause(pause_video_);
+
+  connection_->set_video_feedback_stub(
+      video_frame_pump_->video_feedback_stub());
 }
 
 void ClientSession::SetGnubbyAuthHandlerForTesting(