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 
OPS.endAnnotation,
          ]);
          expect(opList.argsArray[3][0][0].fontChar).toEqual("✔");
          done();
        })
        .catch(done.fail);
    });
    it("should render checkboxes for printing", function (done) {
      const appearanceStatesDict = new Dict();
      const normalAppearanceDict = new Dict();
      const checkedAppearanceDict = new Dict();
      const uncheckedAppearanceDict = new Dict();
      const checkedStream = new StringStream("0.1 0.2 0.3 rg");
      checkedStream.dict = checkedAppearanceDict;
      const uncheckedStream = new StringStream("0.3 0.2 0.1 rg");
      uncheckedStream.dict = uncheckedAppearanceDict;
      checkedAppearanceDict.set("BBox", [0, 0, 8, 8]);
      checkedAppearanceDict.set("FormType", 1);
      checkedAppearanceDict.set("Matrix", [1, 0, 0, 1, 0, 0]);
      normalAppearanceDict.set("Checked", checkedStream);
      normalAppearanceDict.set("Off", uncheckedStream);
      appearanceStatesDict.set("N", normalAppearanceDict);
      buttonWidgetDict.set("AP", appearanceStatesDict);
      const buttonWidgetRef = Ref.get(124, 0);
      const xref = new XRefMock([
        { ref: buttonWidgetRef, data: buttonWidgetDict },
      ]);
      const task = new WorkerTask("test print");
      AnnotationFactory.create(
        xref,