[NOT FOR REVIEW][PPAPI] Implement MediaStreamVideoTrack pepper API

ppapi/cpp/media_stream_video_track.h

Index: ppapi/cpp/media_stream_video_track.h
diff --git a/ppapi/cpp/media_stream_video_track.h b/ppapi/cpp/media_stream_video_track.h
index 4151077a09188907b966c269e31f9e0b7235b064..06deb39f7f5b68c4f5eeb4d7ecc2de304c136501 100644
--- a/ppapi/cpp/media_stream_video_track.h
+++ b/ppapi/cpp/media_stream_video_track.h
@@ -78,10 +78,6 @@ class MediaStreamVideoTrack : public Resource {
   /// <code>PP_OK_COMPLETIONPENDING</code> will be returned immediately and the
   /// <code>callback</code> will be called, when a new frame is received or some
   /// error happens.
-  /// If the caller holds a frame returned by the previous call of
-  /// <code>GetFrame()</code>, <code>PP_ERROR_INPROGRESS</code> will be
-  /// returned. The caller should recycle the previous frame before getting
-  /// the next frame.
   ///
   /// @param[in] callback A <code>PP_CompletionCallback</code> to be called upon
   /// completion of <code>GetFrame()</code>. If success, a VideoFrame will be