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 
done();
      }, done.fail);
    });
    it("should convert the field value to an array", function (done) {
      const inputs = [null, "Foo", ["Foo", "Bar"]];
      const outputs = [[], ["Foo"], ["Foo", "Bar"]];
      let promise = Promise.resolve();
      for (let i = 0, ii = inputs.length; i < ii; i++) {
        promise = promise.then(() => {
          choiceWidgetDict.set("V", inputs[i]);
          const choiceWidgetRef = Ref.get(968, 0);
          const xref = new XRefMock([
            { ref: choiceWidgetRef, data: choiceWidgetDict },
          ]);
          return AnnotationFactory.create(
            xref,
            choiceWidgetRef,
            pdfManagerMock,
            idFactoryMock
          ).then(({ data }) => {
            expect(data.annotationType).toEqual(AnnotationType.WIDGET);
            expect(data.fieldValue).toEqual(outputs[i]);
          });
        });
      }
      promise.then(done, done.fail);
    });
    it("should handle unknown flags", function (done) {
      const choiceWidgetRef = Ref.get(166, 0);
      const xref = new XRefMock([