havingSize(e) {
    return this.size === e && this.textSize === e ? this : this.extend({
      style: this.style.text(),
      size: e,
      textSize: e,
      sizeMultiplier: Z1[e - 1]
    });
  }
Return an options object with the given size and in at least `\textstyle`.
Returns `this` if appropriate.