Add support for content hints to VideoTrack.

webrtc/api/mediastreaminterface.h

 /*
  *  Copyright 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 115 matching lines @@
   virtual bool GetStats(Stats* stats) = 0;
 
  protected:
   virtual ~VideoTrackSourceInterface() {}
 };
 
 class VideoTrackInterface
     : public MediaStreamTrackInterface,
       public rtc::VideoSourceInterface<VideoFrame> {
  public:
+  // Video track content hint, used to override the source is_screencast
+  // property.
+  // See https://crbug.com/653531 and https://github.com/WICG/mst-content-hint.
+  enum class ContentHint { kNone, kFluid, kDetailed };
+
   // Register a video sink for this track.
   void AddOrUpdateSink(rtc::VideoSinkInterface<VideoFrame>* sink,
-                       const rtc::VideoSinkWants& wants) override{};
-  void RemoveSink(rtc::VideoSinkInterface<VideoFrame>* sink) override{};
+                       const rtc::VideoSinkWants& wants) override {}
+  void RemoveSink(rtc::VideoSinkInterface<VideoFrame>* sink) override {}
 
   virtual VideoTrackSourceInterface* GetSource() const = 0;
 
+  virtual ContentHint content_hint() const { return ContentHint::kNone; }
+  virtual void set_content_hint(ContentHint hint) {}
+
  protected:
   virtual ~VideoTrackInterface() {}
 };
 
 // Interface for receiving audio data from a AudioTrack.
 class AudioTrackSinkInterface {
  public:
   virtual void OnData(const void* audio_data,
                       int bits_per_sample,
                       int sample_rate,
@@ skipping 111 matching lines @@
   virtual bool RemoveTrack(AudioTrackInterface* track) = 0;
   virtual bool RemoveTrack(VideoTrackInterface* track) = 0;
 
  protected:
   virtual ~MediaStreamInterface() {}
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_MEDIASTREAMINTERFACE_H_