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 actionDict = new Dict();
          actionDict.set("Type", Name.get("Action"));
          actionDict.set("S", Name.get("JavaScript"));
          actionDict.set("JS", jsEntry);
          const annotationDict = new Dict();
          annotationDict.set("Type", Name.get("Annot"));
          annotationDict.set("Subtype", Name.get("Link"));
          annotationDict.set("A", actionDict);
          const annotationRef = Ref.get(46, 0);
          const xref = new XRefMock([
            { ref: annotationRef, data: annotationDict },
          ]);
          return AnnotationFactory.create(
            xref,
            annotationRef,
            pdfManagerMock,
            idFactoryMock
          ).then(({ data }) => {
            expect(data.annotationType).toEqual(AnnotationType.LINK);
            expect(data.url).toEqual(expectedUrl);
            expect(data.unsafeUrl).toEqual(expectedUnsafeUrl);
            expect(data.dest).toBeUndefined();
            expect(data.newWindow).toEqual(expectedNewWindow);
          });
        }
        
        const annotation1 = checkJsAction({
          jsEntry: 'function someFun() { return "qwerty"; } someFun();',
          expectedUrl: undefined,
          expectedUnsafeUrl: undefined,