MediaStreamVideoSource exports current video format

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 69 matching lines @@
                 const blink::WebMediaConstraints& constraints,
                 const ConstraintsCallback& callback);
   void RemoveTrack(MediaStreamVideoTrack* track);
 
   // Return true if |name| is a constraint supported by MediaStreamVideoSource.
   static bool IsConstraintSupported(const std::string& name);
 
   // Returns the task runner where video frames will be delivered on.
   base::SingleThreadTaskRunner* io_task_runner() const;
 
+  media::VideoCaptureFormat current_format() const { return current_format_; }

[miu, 2016/02/05 22:20:47]

The format is invalid until the source is started.  Also, there are
thread-safety concerns here.  IMO, I think the method should look something like
the following:

  // Returns the current video format of this source, or null if it has not yet
been determined.
  const media::VideoCaptureFormat* current_format() const {
    DCHECK(CalledOnValidThread());
    if (state_ == STARTING || state_ == STARTED)
      return &current_format_;
    return nullptr;
  }

[miu, 2016/02/05 22:20:47]

Where is the code that calls this?  Note that there's a danger this method could
be removed if a project member does not see it being called from anywhere.  You
should probably just punt on this code review, and include this new method in
the change where you have code that calls it.

[Mikhail, 2016/02/08 08:13:06]

I will reference this CL when upload the client code. thanks

+
  protected:
   void DoStopSource() override;
 
   // Sets ready state and notifies the ready state to all registered tracks.
   virtual void SetReadyState(blink::WebMediaStreamSource::ReadyState state);
 
   // Sets muted state and notifies it to all registered tracks.
   virtual void SetMutedState(bool state);
 
   // An implementation must fetch the formats that can currently be used by
@@ skipping 83 matching lines @@
 
   // 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_