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 
"(Lorem ipsum dolor sit amet, consectetur adipiscing elit.) Tj\n" +
        "0.00 -5.00 Td " +
        "(Aliquam vitae felis ac lectus bibendum ultricies quis non) Tj\n" +
        "0.00 -5.00 Td " +
        "( diam.) Tj\n" +
        "0.00 -5.00 Td " +
        "(Morbi id rttitor quam, a iaculis dui.) Tj\n" +
        "0.00 -5.00 Td " +
        "(Pellentesque habitant morbi tristique senectus et netus ) Tj\n" +
        "0.00 -5.00 Td " +
        "(et malesuada fames ac turpis egestas.) Tj\n" +
        "0.00 -5.00 Td () Tj\n" +
        "0.00 -5.00 Td () Tj\n" +
        "0.00 -5.00 Td " +
        "(Nulla consectetur, ligula in tincidunt placerat, velit ) Tj\n" +
        "0.00 -5.00 Td " +
        "(augue consectetur orci, sed mattis libero nunc ut massa.) Tj\n" +
        "0.00 -5.00 Td " +
        "(Etiam facilisis tempus interdum.) Tj ET Q EMC";
      AnnotationFactory.create(
        xref,
        textWidgetRef,
        pdfManagerMock,
        idFactoryMock
      )
        .then(annotation => {
          const id = annotation.data.id;
          const annotationStorage = {};
          annotationStorage[id] = {
            value: