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 isRenderable = !!(
      parameters.data.url ||
      parameters.data.dest ||
      parameters.data.action ||
      parameters.data.isTooltipOnly ||
      (parameters.data.actions &&
        (parameters.data.actions.Action ||
          parameters.data.actions.MouseUp ||
          parameters.data.actions.MouseDown))
    );
    super(parameters, { isRenderable, createQuadrilaterals: true });
  }
  render() {
    const { data, linkService } = this;
    const link = document.createElement("a");
    if (data.url) {
      addLinkAttributes(link, {
        url: data.url,
        target: data.newWindow
          ? LinkTarget.BLANK
          : linkService.externalLinkTarget,
        rel: linkService.externalLinkRel,
        enabled: linkService.externalLinkEnabled,
      });
    } else if (data.action) {
      this._bindNamedAction(link, data.action);
    } else if (data.dest) {
      this._bindLink(link, data.dest);
    } else if (
      data.actions &&