Reading from the source code:

https://github.com/mozilla/pdf.js/blob/57d196e3497e77c81c19f852715ce79d9fb91492/src/display/annotation_layer.js#L2846

it appears to me it was not an intention to mark downloadManager as a required parameter in AnnotationLayerParameters:

https://github.com/mozilla/pdf.js/blob/57d196e3497e77c81c19f852715ce79d9fb91492/src/display/annotation_layer.js#L63

and AnnotationLayerBuilderOptions:

https://github.com/mozilla/pdf.js/blob/57d196e3497e77c81c19f852715ce79d9fb91492/web/annotation_layer_builder.js#L40

and it should be optional, similarly to accessibilityManager for example:

https://github.com/mozilla/pdf.js/blob/57d196e3497e77c81c19f852715ce79d9fb91492/web/text_layer_builder.js#L30

**Configuration:**
- PDF.js version: 2.11.174
- Is a browser extension: no

**What is the expected behavior? (add screenshot)**

`downloadManager` to be optional

**What went wrong? (add screenshot)**

`downloadManager` marked as required

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

constructor(parameters) {
    super(parameters, { ignoreBorder: parameters.data.hasAppearance });
  }
  render() {
    
    
    
    const container = super.render();
    container.classList.add("buttonWidgetAnnotation", "pushButton");
    if (this.data.alternativeText) {
      container.title = this.data.alternativeText;
    }
    const linkElement = container.lastChild;
    if (this.enableScripting && this.hasJSActions && linkElement) {
      this._setDefaultPropertiesFromJS(linkElement);
      linkElement.addEventListener("updatefromsandbox", jsEvent => {
        this._dispatchEventFromSandbox({}, jsEvent);
      });
    }
    return container;
  }
}
class ChoiceWidgetAnnotationElement extends WidgetAnnotationElement {
  constructor(parameters) {