static parseTime_(string) {
    const SsaTextParser = shaka.text.SsaTextParser;
    const match = SsaTextParser.timeFormat_.exec(string);
    const hours = match[1] ? parseInt(match[1].replace(':', ''), 10) : 0;
    const minutes = parseInt(match[2], 10);
    const seconds = parseFloat(match[3]);
    return hours * 3600 + minutes * 60 + seconds;
  }
Parses a SSA time from the given parser.

@param {string} string
@return {number}
@private