sendMediaStatus_(requestId = 0, media = null) {
    const mediaStatus = {
      // mediaSessionId is a unique ID for the playback of this specific
      // session.
      // It's used to identify a specific instance of a playback.
      // We don't support multiple playbacks, so just return 0.
      'mediaSessionId': 0,
      'playbackRate': this.video_.playbackRate,
      'playerState': this.getPlayState_(),
      'currentTime': this.video_.currentTime,
      // supportedMediaCommands is a sum of all the flags of commands that the
      // player supports.
      // The list of commands with respective flags is:
      // 1 - Pause
      // 2 - Seek
      // 4 - Stream volume
      // 8 - Stream mute
      // 16 - Skip forward
      // 32 - Skip backward
      // We support all of them, and their sum is 63.
      'supportedMediaCommands': 63,
      'volume': {
        'level': this.video_.volume,
        'muted': this.video_.muted,
      },
    };

    if (media) {
      mediaStatus['media'] = media;
    }

    const ret = {
      'requestId': requestId,
      'type': 'MEDIA_STATUS',
      'status': [mediaStatus],
    };

    this.sendMessage_(ret, this.genericBus_);
  }
@param {number=} requestId
@param {Object=} media
@private