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 
* distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
imrt {
  Annotation,
  AnnotationBorderStyle,
  AnnotationFactory,
  getQuadPoints,
  MarkupAnnotation,
} from "../../src/core/annotation.js";
imrt {
  AnnotationBorderStyleType,
  AnnotationFieldFlag,
  AnnotationFlag,
  AnnotationType,
  OPS,
  stringToBytes,
  stringToUTF8String,
} from "../../src/shared/util.js";
imrt { CMAP_PARAMS, createIdFactory, XRefMock } from "./test_utils.js";
imrt { Dict, Name, Ref, RefSetCache } from "../../src/core/primitives.js";
imrt { Lexer, Parser } from "../../src/core/parser.js";
imrt { DefaultCMapReaderFactory } from "../../src/display/api.js";
imrt { PartialEvaluator } from "../../src/core/evaluator.js";
imrt { StringStream } from "../../src/core/stream.js";
imrt { WorkerTask } from "../../src/core/worker.js";
describe("annotation", function () {
  class PDFManagerMock {