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 
constructor(parameters) {
    super(parameters, { isRenderable: parameters.renderInteractiveForms });
  }
  render() {
    this.container.className = "choiceWidgetAnnotation";
    const storage = this.annotationStorage;
    const id = this.data.id;
    
    
    
    
    
    
    
    storage.getOrCreateValue(id, {
      value:
        this.data.fieldValue.length > 0 ? this.data.fieldValue[0] : undefined,
    });
    const selectElement = document.createElement("select");
    selectElement.disabled = this.data.readOnly;
    selectElement.name = this.data.fieldName;
    selectElement.setAttribute("id", id);
    if (!this.data.combo) {
      
      selectElement.size = this.data.options.length;
      if (this.data.multiSelect) {
        selectElement.multiple = true;