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 
const color = detail.strokeColor;
              event.target.style.color = ColorConverters[`${color[0]}_HTML`](
                color.slice(1)
              );
            },
          };
          Object.keys(detail)
            .filter(name => name in actions)
            .forEach(name => actions[name]());
        });
        if (this.data.actions) {
          
          
          element.addEventListener("keydown", event => {
            elementData.beforeInputValue = event.target.value;
            
            
            let commitKey = -1;
            if (event.key === "Escape") {
              commitKey = 0;
            } else if (event.key === "Enter") {
              commitKey = 2;
            } else if (event.key === "Tab") {
              commitKey = 3;
            }
            if (commitKey === -1) {
              return;
            }