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 
}
    this.container.append(svg);
    return this.container;
  }
}
class HighlightAnnotationElement extends AnnotationElement {
  constructor(parameters) {
    const isRenderable = !!(
      parameters.data.hasPopup ||
      parameters.data.title ||
      parameters.data.contents
    );
    super(parameters, {
      isRenderable,
      ignoreBorder: true,
      createQuadrilaterals: true,
    });
  }
  render() {
    if (!this.data.hasPopup) {
      this._createPopup(null, this.data);
    }
    if (this.quadrilaterals) {
      return this._renderQuadrilaterals("highlightAnnotation");
    }
    this.container.className = "highlightAnnotation";
    return this.container;
  }
}
class UnderlineAnnotationElement extends AnnotationElement {