Change a disabled MediaStreamVideoTrack to output black video frames for each incoming frame.

content/renderer/media/rtc_video_renderer.h

 // Copyright (c) 2012 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 CONTENT_RENDERER_MEDIA_RTC_VIDEO_RENDERER_H_
 #define CONTENT_RENDERER_MEDIA_RTC_VIDEO_RENDERER_H_
 
 #include "base/callback.h"
 #include "base/memory/weak_ptr.h"
 #include "content/common/content_export.h"
@@ skipping 43 matching lines @@
     STOPPED,
   };
 
   void OnVideoFrame(const scoped_refptr<media::VideoFrame>& frame,
                     const media::VideoCaptureFormat& format,
                     const base::TimeTicks& estimated_capture_time);
 
   // VideoTrackSink implementation. Called on the main thread.
   virtual void OnReadyStateChanged(
       blink::WebMediaStreamSource::ReadyState state) OVERRIDE;
-  virtual void OnEnabledChanged(bool enabled) OVERRIDE;
 
   void RenderSignalingFrame();
 
   base::Closure error_cb_;
   RepaintCB repaint_cb_;
   scoped_refptr<base::MessageLoopProxy> message_loop_proxy_;
   State state_;
   gfx::Size frame_size_;
   blink::WebMediaStreamTrack video_track_;
   base::WeakPtrFactory<RTCVideoRenderer> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(RTCVideoRenderer);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_RTC_VIDEO_RENDERER_H_