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

remoting/protocol/video_stream.h

 // Copyright 2015 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.
 
 #ifndef REMOTING_PROTOCOL_VIDEO_STREAM_H_
 #define REMOTING_PROTOCOL_VIDEO_STREAM_H_
 
 #include <stdint.h>
 
 #include <cstdint>
 
 #include "base/callback_forward.h"
 
 namespace webrtc {
 class DesktopSize;
 class DesktopVector;
 }  // namespace webrtc
 
 namespace remoting {
 namespace protocol {
 
 class VideoStream {
  public:
-  // Callback used to notify about screen size changes. The size must be
-  // specified in physical pixels.
-  typedef base::Callback<void(const webrtc::DesktopSize& size,
-                              const webrtc::DesktopVector& dpi)>
-      SizeCallback;
+  class Observer {
+   public:
+    // Called to notify about screen size changes. The size is specified in
+    // physical pixels.
+    virtual void OnVideoSizeChanged(VideoStream* stream,
+                                    const webrtc::DesktopSize& size,
+                                    const webrtc::DesktopVector& dpi) = 0;
+
+    // Called to notify about an outgoing video frame. |input_event_timestamp|
+    // corresponds to the last input event that was injected before the frame
+    // was captured.
+    virtual void OnVideoFrameSent(VideoStream* stream,
+                                  uint32_t frame_id,
+                                  int64_t event_timestamp) = 0;
+  };
 
   VideoStream() {}
   virtual ~VideoStream() {}
 
   // Pauses or resumes scheduling of frame captures. Pausing/resuming captures
   // only affects capture scheduling and does not stop/start the capturer.
   virtual void Pause(bool pause) = 0;
 
   // Should be called whenever an input event is received.
   virtual void OnInputEventReceived(int64_t event_timestamp) = 0;
 
   // Sets whether the video encoder should be requested to encode losslessly,
   // or to use a lossless color space (typically requiring higher bandwidth).
   virtual void SetLosslessEncode(bool want_lossless) = 0;
   virtual void SetLosslessColor(bool want_lossless) = 0;
 
-  // Sets SizeCallback to be called when screen size is changed.
-  virtual void SetSizeCallback(const SizeCallback& size_callback) = 0;
+  // Sets stream observer.
+  virtual void SetObserver(Observer* observer) = 0;
 };
 
 }  // namespace protocol
 }  // namespace remoting
 
 #endif  // REMOTING_PROTOCOL_VIDEO_STREAM_H_