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 
idFactoryMock
      ).then(({ data }) => {
        expect(data.url).toEqual("https://developer.mozilla.org/en-US/");
        done();
      }, done.fail);
    });
  });
  describe("ChoiceWidgetAnnotation", function () {
    let choiceWidgetDict, fontRefObj;
    beforeEach(function (done) {
      choiceWidgetDict = new Dict();
      choiceWidgetDict.set("Type", Name.get("Annot"));
      choiceWidgetDict.set("Subtype", Name.get("Widget"));
      choiceWidgetDict.set("FT", Name.get("Ch"));
      const helvDict = new Dict();
      helvDict.set("BaseFont", Name.get("Helvetica"));
      helvDict.set("Type", Name.get("Font"));
      helvDict.set("Subtype", Name.get("Type1"));
      const fontRef = Ref.get(314, 0);
      fontRefObj = { ref: fontRef, data: helvDict };
      const resourceDict = new Dict();
      const fontDict = new Dict();
      fontDict.set("Helv", fontRef);
      resourceDict.set("Font", fontDict);
      choiceWidgetDict.set("DA", "/Helv 5 Tf");
      choiceWidgetDict.set("DR", resourceDict);
      choiceWidgetDict.set("Rect", [0, 0, 32, 10]);
      done();
    });
    afterEach(function () {