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

remoting/protocol/video_frame_pump.cc

Index: remoting/protocol/video_frame_pump.cc
diff --git a/remoting/protocol/video_frame_pump.cc b/remoting/protocol/video_frame_pump.cc
index e2882ad7613f188d761d3860725e8ad018c5c442..c68fff84d5ba41cfabcf25543b2d9b1ae228e694 100644
--- a/remoting/protocol/video_frame_pump.cc
+++ b/remoting/protocol/video_frame_pump.cc
@@ -107,9 +107,9 @@ void VideoFramePump::SetLosslessColor(bool want_lossless) {
                             base::Unretained(encoder_.get()), want_lossless));
 }
 
-void VideoFramePump::SetSizeCallback(const SizeCallback& size_callback) {
+void VideoFramePump::SetObserver(Observer* observer) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  size_callback_ = size_callback;
+  observer_ = observer;
 }
 
 void VideoFramePump::OnCaptureResult(
@@ -128,8 +128,8 @@ void VideoFramePump::OnCaptureResult(
     if (!frame_size_.equals(frame->size()) || !frame_dpi_.equals(dpi)) {
       frame_size_ = frame->size();
       frame_dpi_ = dpi;
-      if (!size_callback_.is_null())
-        size_callback_.Run(frame_size_, frame_dpi_);
+      if (observer_)
+        observer_->OnVideoSizeChanged(this, frame_size_, frame_dpi_);
     }
   }
 
@@ -208,6 +208,12 @@ void VideoFramePump::SendPacket(std::unique_ptr<PacketWithTimestamps> packet) {
   packet->timestamps->can_send_time = base::TimeTicks::Now();
   UpdateFrameTimers(packet->packet.get(), packet->timestamps.get());
 
+  if (observer_) {
+    observer_->OnVideoFrameSent(
+        this, packet->packet->frame_id(),
+        packet->timestamps->input_event_client_timestamp);
+  }
+
   send_pending_ = true;
   video_stub_->ProcessVideoPacket(std::move(packet->packet),
                                   base::Bind(&VideoFramePump::OnVideoPacketSent,