Video Capture: Allow suspension of individual devices.

content/renderer/media/media_stream_video_source.h

 // Copyright 2014 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_MEDIA_STREAM_VIDEO_SOURCE_H_
 #define CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_SOURCE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 53 matching lines @@
   static MediaStreamVideoSource* GetVideoSource(
       const blink::WebMediaStreamSource& source);
 
   // Puts |track| in the registered tracks list.
   void AddTrack(MediaStreamVideoTrack* track,
                 const VideoCaptureDeliverFrameCB& frame_callback,
                 const blink::WebMediaConstraints& constraints,
                 const ConstraintsCallback& callback);
   void RemoveTrack(MediaStreamVideoTrack* track);
 
+  // Called by |track| to notify the source whether it has any paths to a
+  // consuming endpoint.
+  void UpdateHasConsumers(MediaStreamVideoTrack* track, bool has_consumers);
+
   void UpdateCapturingLinkSecure(MediaStreamVideoTrack* track, bool is_secure);
 
   // Request underlying source to capture a new frame.
   virtual void RequestRefreshFrame() {}
 
-  // Notify underlying source if the capturing link is secure.
-  virtual void SetCapturingLinkSecured(bool is_secure) {}
-
   // Returns the task runner where video frames will be delivered on.
   base::SingleThreadTaskRunner* io_task_runner() const;
 
   const media::VideoCaptureFormat* GetCurrentFormat() const;
 
   base::WeakPtr<MediaStreamVideoSource> GetWeakPtr() {
     return weak_factory_.GetWeakPtr();
   }
 
  protected:
@@ skipping 27 matching lines @@
       const media::VideoCaptureFormat& format,
       const blink::WebMediaConstraints& constraints,
       const VideoCaptureDeliverFrameCB& frame_callback) = 0;
   void OnStartDone(MediaStreamRequestResult result);
 
   // An implementation must immediately stop capture video frames and must not
   // call OnSupportedFormats after this method has been called. After this
   // method has been called, MediaStreamVideoSource may be deleted.
   virtual void StopSourceImpl() = 0;
 
+  // Optionally overridden by subclasses to act on whether there are any
+  // consumers present. When none are present, the source can stop delivering
+  // frames, giving it the option of running in an "idle" state to minimize
+  // resource usage.
+  virtual void OnHasConsumers(bool has_consumers) {}
+
+  // Optionally overridden by subclasses to act on whether the capturing link
+  // has become secure or insecure.
+  virtual void OnCapturingLinkSecured(bool is_secure) {}
+
   enum State {
     NEW,
     RETRIEVING_CAPABILITIES,
     STARTING,
     STARTED,
     ENDED
   };
   State state() const { return state_; }
 
  private:
@@ skipping 37 matching lines @@
   std::vector<TrackDescriptor> track_descriptors_;
 
   media::VideoCaptureFormats supported_formats_;
 
   // |track_adapter_| delivers video frames to the tracks on the IO-thread.
   const scoped_refptr<VideoTrackAdapter> track_adapter_;
 
   // Tracks that currently are connected to this source.
   std::vector<MediaStreamVideoTrack*> tracks_;
 
+  // Tracks that have no paths to a consuming endpoint, and so do not need
+  // frames delivered from the source. This is a subset of |tracks_|.
+  std::vector<MediaStreamVideoTrack*> suspended_tracks_;
+
   // This is used for tracking if all connected video sinks are secure.
   SecureDisplayLinkTracker<MediaStreamVideoTrack> secure_tracker_;
 
   // NOTE: Weak pointers must be invalidated before all other member variables.
   base::WeakPtrFactory<MediaStreamVideoSource> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(MediaStreamVideoSource);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_MEDIA_MEDIA_STREAM_VIDEO_SOURCE_H_