hdlr_(streamInfo) {
    const Mp4Generator = shaka.util.Mp4Generator;
    const ContentType = shaka.util.ManifestParserUtils.ContentType;
    let bytes = new Uint8Array([]);
    switch (streamInfo.type) {
      case ContentType.VIDEO:
        bytes = Mp4Generator.HDLR_TYPES_.video;
        break;
      case ContentType.AUDIO:
        bytes = Mp4Generator.HDLR_TYPES_.audio;
        break;
    }
    return Mp4Generator.box('hdlr', bytes);
  }
Generate a HDLR box

@param {shaka.util.Mp4Generator.StreamInfo} streamInfo
@return {!Uint8Array}
@private