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 
` 2.00 2.00 Td (${utf16String}) Tj ET Q EMC`
          );
          done();
        }, done.fail);
    });
    it("should render regular text for printing using normal appearance", function (done) {
      const textWidgetRef = Ref.get(271, 0);
      const appearanceStatesDict = new Dict();
      const normalAppearanceDict = new Dict();
      const normalAppearanceStream = new StringStream("0.1 0.2 0.3 rg");
      normalAppearanceStream.dict = normalAppearanceDict;
      appearanceStatesDict.set("N", normalAppearanceStream);
      textWidgetDict.set("AP", appearanceStatesDict);
      const xref = new XRefMock([
        { ref: textWidgetRef, data: textWidgetDict },
        helvRefObj,
      ]);
      const task = new WorkerTask("test print");
      partialEvaluator.xref = xref;
      AnnotationFactory.create(
        xref,
        textWidgetRef,
        pdfManagerMock,
        idFactoryMock
      )
        .then(annotation => {
          const annotationStorage = {};
          return annotation.getOperatorList(
            partialEvaluator,
            task,