clone({
    scale = this.scale,
    rotation = this.rotation,
    offsetX = this.offsetX,
    offsetY = this.offsetY,
    dontFlip = false,
  } = {}) {
    return new PageViewport({
      viewBox: this.viewBox.slice(),
      userUnit: this.userUnit,
      scale,
      rotation,
      offsetX,
      offsetY,
      dontFlip,
    });
  }
Clones viewport, with optional additional properties.
@param {PageViewportCloneParameters} [params]
@returns {PageViewport} Cloned viewport.