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 
return isSettled;
    },
  });
  capability.promise = new Promise(function (resolve, reject) {
    capability.resolve = function (data) {
      isSettled = true;
      resolve(data);
    };
    capability.reject = function (reason) {
      isSettled = true;
      reject(reason);
    };
  });
  return capability;
}
const createObjectURL = (function createObjectURLClosure() {
  
  const digits =
    "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
  
  return function createObjectURL(data, contentType, forceDataSchema = false) {
    if (!forceDataSchema && URL.createObjectURL) {
      const blob = new Blob([data], { type: contentType });
      return URL.createObjectURL(blob);
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    let buffer = `data:${contentType};base64,`;
    for (let i = 0, ii = data.length; i < ii; i += 3) {
      const b1 = data[i] & 0xff;
      const b2 = data[i + 1] & 0xff;
      const b3 = data[i + 2] & 0xff;