clampTime_(time) {
    const seekable = this.mediaElement_.seekable;
    if (seekable.length > 0) {
      time = Math.max(seekable.start(0), time);
      time = Math.min(seekable.end(seekable.length - 1), time);
    }
    return time;
  }
@param {number} time
@return {number}
@private