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 
"123 0 obj\n" +
              "<< /Type /Annot /Subtype /Widget /FT /Ch /DA (/Helv 5 Tf) /DR " +
              "<< /Font << /Helv 314 0 R>>>> " +
              "/Rect [0 0 32 10] /Opt [(A) (B) (C)] /V (C) " +
              "/AP << /N 1 0 R>> /M (date)>>\nendobj\n"
          );
          expect(newData.data).toEqual(
            "1 0 obj\n" +
              "<< /Length 67 /Subtype /Form /Resources << /Font << /Helv 314 0 R>>>> " +
              "/BBox [0 0 32 10]>> stream\n" +
              "/Tx BMC q BT /Helv 5 Tf 1 0 0 1 0 0 Tm 2.00 2.00 Td (C) Tj ET Q EMC\n" +
              "endstream\nendobj\n"
          );
          done();
        }, done.fail);
    });
  });
  describe("LineAnnotation", function () {
    it("should set the line coordinates", function (done) {
      const lineDict = new Dict();
      lineDict.set("Type", Name.get("Annot"));
      lineDict.set("Subtype", Name.get("Line"));
      lineDict.set("L", [1, 2, 3, 4]);
      const lineRef = Ref.get(122, 0);
      const xref = new XRefMock([{ ref: lineRef, data: lineDict }]);
      AnnotationFactory.create(
        xref,
        lineRef,
        pdfManagerMock,
        idFactoryMock