MediaStream 构造函数

实现

factory MediaStream([stream_OR_tracks]) {
  if (stream_OR_tracks == null) {
    return MediaStream._create_1();
  }
  if ((stream_OR_tracks is MediaStream)) {
    return MediaStream._create_2(stream_OR_tracks);
  }
  if ((stream_OR_tracks is List<MediaStreamTrack>)) {
    return MediaStream._create_3(stream_OR_tracks);
  }
  throw new ArgumentError("Incorrect number or type of arguments");
}