Replace VideoStream::SizeCallback with VideoStream::Observer interface.

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 dc40047992085e5868630c803d01801acc3fc5d5..99c7ed509963a449f2a799cf36e044f4d7cbe00c 100644
--- a/remoting/host/client_session.cc
+++ b/remoting/host/client_session.cc
@@ -293,8 +293,7 @@ void ClientSession::CreateVideoStreams(
   video_stream_ = connection_->StartVideoStream(
       desktop_environment_->CreateVideoCapturer());
 
-  video_stream_->SetSizeCallback(
-      base::Bind(&ClientSession::OnScreenSizeChanged, base::Unretained(this)));
+  video_stream_->SetObserver(this);
 
   // Apply video-control parameters to the new stream.
   video_stream_->SetLosslessEncode(lossless_video_encode_);
@@ -434,8 +433,9 @@ std::unique_ptr<protocol::ClipboardStub> ClientSession::CreateClipboardProxy() {
                                          base::ThreadTaskRunnerHandle::Get()));
 }
 
-void ClientSession::OnScreenSizeChanged(const webrtc::DesktopSize& size,
-                                        const webrtc::DesktopVector& dpi) {
+void ClientSession::OnVideoSizeChanged(protocol::VideoStream* video_stream,
+                                       const webrtc::DesktopSize& size,
+                                       const webrtc::DesktopVector& dpi) {
   DCHECK(CalledOnValidThread());
 
   mouse_clamping_filter_.set_output_size(size);
@@ -476,4 +476,10 @@ void ClientSession::OnScreenSizeChanged(const webrtc::DesktopSize& size,
   }
 }
 
+void ClientSession::OnVideoFrameSent(protocol::VideoStream* stream,
+                                     uint32_t frame_id,
+                                     int64_t input_event_timestamp) {
+  // TODO(sergeyu): Send a message to the client to notify about the new frame.
+}
+
 }  // namespace remoting