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 
}
    } else {
      if (start < i) {
        buffer.push(str.substring(start, i));
      }
      buffer.push(`&#x${char.toString(16).toUpperCase()};`);
      if (char > 0xd7ff && (char < 0xe000 || char > 0xfffd)) {
        
        i++;
      }
      start = i + 1;
    }
  }
  if (buffer.length === 0) {
    return str;
  }
  if (start < str.length) {
    buffer.push(str.substring(start, str.length));
  }
  return buffer.join("");
}
export {
  AbortException,
  AnnotationActionEventType,
  AnnotationBorderStyleType,
  AnnotationFieldFlag,
  AnnotationFlag,
  AnnotationMarkedState,
  AnnotationReplyType,
  AnnotationReviewState,