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 
const IGNORE_TYPES = [
      "Line",
      "Square",
      "Circle",
      "PolyLine",
      "Polygon",
      "Ink",
    ];
    this.container.className = "popupAnnotation";
    if (IGNORE_TYPES.includes(this.data.parentType)) {
      return this.container;
    }
    const selector = `[data-annotation-id="${this.data.parentId}"]`;
    const parentElements = this.layer.querySelectorAll(selector);
    if (parentElements.length === 0) {
      return this.container;
    }
    const popup = new PopupElement({
      container: this.container,
      trigger: Array.from(parentElements),
      color: this.data.color,
      title: this.data.title,
      modificationDate: this.data.modificationDate,
      contents: this.data.contents,
    });