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 
pupDict.set("Parent", parentDict);
        const pupRef = Ref.get(13, 0);
        const xref = new XRefMock([{ ref: pupRef, data: pupDict }]);
        AnnotationFactory.create(
          xref,
          pupRef,
          pdfManagerMock,
          idFactoryMock
        ).then(({ data, viewable }) => {
          expect(data.annotationType).toEqual(AnnotationType.POPUP);
          // We should not modify the `annotationFlags` returned through
          // e.g., the API.
          expect(data.annotationFlags).toEqual(25);
          // The pup should able` property of the parent.
          expect(viewable).toEqual(true);
          done();
        }, done.fail);
      }
    );
    it(
      "should correctly inherit Contents from group-master annotation " +
        "if parent has ReplyType == Group",
      function (done) {
        const annotationRef = Ref.get(819, 0);
        const annotationDict = new Dict();
        annotationDict.set("Type", Name.get("Annot"));
        annotationDict.set("Subtype", Name.get("Text"));
        annotationDict.set("T", "Correct Title");
        annotationDict.set("Contents", "Correct Text");
        annotationDict.set("M", "D:20190423");