In the following spots a "MouseUp" eventName is being used, which does look inconsistent considering that the "Mouse Down"/"Mouse Enter"/"Mouse Exit" eventNames all have a space in them.
Is this inconsistency actually expected, or is it a simple typo? If the former, then a comment explaining *why* would be appropriate; otherwise we should just fix this :-)

 - https://github.com/mozilla/pdf.js/blob/25b84ce84c95ba06d1ee57e578672048269c39c1/src/display/annotation_layer.js#L806

 - https://github.com/mozilla/pdf.js/blob/25b84ce84c95ba06d1ee57e578672048269c39c1/src/display/annotation_layer.js#L945

 - https://github.com/mozilla/pdf.js/blob/25b84ce84c95ba06d1ee57e578672048269c39c1/src/display/annotation_layer.js#L1034

 - https://github.com/mozilla/pdf.js/blob/25b84ce84c95ba06d1ee57e578672048269c39c1/src/display/annotation_layer.js#L1168

/cc @calixteman 
* @private
   * @param {string} className
   * @memberof AnnotationElement
   * @returns {Array<HTMLSectionElement>}
   */
  _renderQuadrilaterals(className) {
    if (
      typeof PDFJSDev === "undefined" ||
      PDFJSDev.test("!PRODUCTION || TESTING")
    ) {
      assert(this.quadrilaterals, "Missing quadrilaterals during rendering");
    }
    this.quadrilaterals.forEach(quadrilateral => {
      quadrilateral.className = className;
    });
    return this.quadrilaterals;
  }
  /**
   * Render the annotation's HTML element(s).
   *
   * @public
   * @memberof AnnotationElement
   * @returns {HTMLSectionElement|Array<HTMLSectionElement>}
   */
  render() {
    unreachable("Abstract method `AnnotationElement.render` called");
  }
}
class LinkAnnotationElement extends AnnotationElement {
  constructor(parameters) {