static html5TextTrackToTrack(textTrack) {
    const ContentType = shaka.util.ManifestParserUtils.ContentType;
    /** @type {shaka.extern.TextTrack} */
    const track = {
      id: shaka.util.StreamUtils.html5TrackId(textTrack),
      active: textTrack.mode != 'disabled',
      type: ContentType.TEXT,
      bandwidth: 0,
      language: shaka.util.LanguageUtils.normalize(textTrack.language || 'und'),
      label: textTrack.label,
      kind: textTrack.kind,
      mimeType: null,
      codecs: null,
      primary: false,
      roles: [],
      accessibilityPurpose: null,
      forced: textTrack.kind == 'forced',
      originalTextId: textTrack.id,
      originalLanguage: textTrack.language,
    };
    if (textTrack.kind == 'captions') {
      // See: https://github.com/shaka-project/shaka-player/issues/6233
      track.mimeType = 'unknown';
    }
    if (textTrack.kind == 'subtitles') {
      track.mimeType = 'text/vtt';
    }
    if (textTrack.kind) {
      track.roles = [textTrack.kind];
    }

    return track;
  }
@param {TextTrack} textTrack
@return {shaka.extern.TextTrack}