Request frame for new sinks from MediaStreamVideoTrack

media/base/video_capturer_source.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 MEDIA_BASE_VIDEO_CAPTURER_SOURCE_H_
 #define MEDIA_BASE_VIDEO_CAPTURER_SOURCE_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 58 matching lines @@
   // argument) if called with the wrong task runner.
   // If capturing fails to start or stopped due to an external event then
   // |running_callback| will be called with a parameter of false.
   // |running_callback| will always be called on the same thread as the
   // StartCapture.
   virtual void StartCapture(
       const media::VideoCaptureParams& params,
       const VideoCaptureDeliverFrameCB& new_frame_callback,
       const RunningCallback& running_callback) = 0;
 
+  // If capturing is started successfully, then |new_frame_callback| should be
+  // called with a frame. Some implementations may hold onto the last frame and
+  // send it.
+  virtual void RequestFrame() {}

[miu, 2016/03/25 22:05:06]

1. Can we name this RequestRefreshFrame() here and in
MediaStreamVideoCapturerSource and MediaStreamVideoSource?  This would make it
consistent with the naming in the browser-side changes:
https://code.google.com/p/chromium/codesearch#chromium/src/media/capture/vide...

2. Also, this comment should probably describe the same semantics and usage
patterns as in the VideoCaptureDevice change (link above).  Meaning, the source
can decide whether to honor the request, depending on whether it will be sending
more frames soon or capture is halted due to unchanging content.

[emircan, 2016/03/25 23:18:41]

1) Done. I was trying to be consistent with RequestFrame() from the W3C spec[0],
but there are multiple users now :)

[0] http://w3c.github.io/mediacapture-fromelement/#dfn-requestframe

2) Done.

+
   // Stops capturing frames and clears all callbacks including the
   // SupportedFormatsCallback callback. Note that queued frame callbacks
   // may still occur after this call, so the caller must take care to
   // use refcounted or weak references in |new_frame_callback|.
   virtual void StopCapture() = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_VIDEO_CAPTURER_SOURCE_H_