static parseVTTC_(data, startTime, endTime) {
    let payload;
    let id;
    let settings;

    new shaka.util.Mp4Parser()
        .box('payl', shaka.util.Mp4Parser.allData((data) => {
          payload = shaka.util.StringUtils.fromUTF8(data);
        }))
        .box('iden', shaka.util.Mp4Parser.allData((data) => {
          id = shaka.util.StringUtils.fromUTF8(data);
        }))
        .box('sttg', shaka.util.Mp4Parser.allData((data) => {
          settings = shaka.util.StringUtils.fromUTF8(data);
        }))
        .parse(data);

    if (payload) {
      return shaka.text.Mp4VttParser.assembleCue_(
          payload, id, settings, startTime, endTime);
    } else {
      return null;
    }
  }
Parses a vttc box into a cue.

@param {!Uint8Array} data
@param {number} startTime
@param {number} endTime
@return {shaka.text.Cue}
@private