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 6fcba24043393680c4f886c56aec15471ae4fffc..cc83feda7361134af836f90f5769ad73db929755 100644
--- a/remoting/host/client_session.cc
+++ b/remoting/host/client_session.cc
@@ -448,6 +448,7 @@ 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
@@ -482,6 +483,9 @@ 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(