static getTrackKind_(track) {
    const device = shaka.device.DeviceFactory.getDevice();
    if (track.forced && device.getBrowserEngine() ===
        shaka.device.IDevice.BrowserEngine.WEBKIT) {
      return 'forced';
    } else if (
      track.kind === 'caption' || (
        track.roles &&
        track.roles.some(
            (role) => role.includes('transcribes-spoken-dialog')) &&
        track.roles.some(
            (role) => role.includes('describes-music-and-sound'))
      )
    ) {
      return 'captions';
    }

    return 'subtitles';
  }
@param {!shaka.extern.TextTrack} track
@return {string}
@private