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 
elementData.userValue = detail.value || "";
              storage.setValue(id, { value: elementData.userValue.toString() });
              if (!elementData.formattedValue) {
                event.target.value = elementData.userValue;
              }
            },
            valueAsString() {
              elementData.formattedValue = detail.valueAsString || "";
              if (event.target !== document.activeElement) {
                
                event.target.value = elementData.formattedValue;
              }
              storage.setValue(id, {
                formattedValue: elementData.formattedValue,
              });
            },
            focus() {