  - Open https://mozilla.github.io/pdf.js/web/viewer.html
  - Open a pdf with some XFA (for example the on in https://github.com/mozilla/pdf.js/issues/13679#issue-937616350)

The pdf is not correctly displayed because `enableXfa` is false.

@Snuffleupagus, the pref is set to true in Firefox nightly, is there anything blocking setting it to true in the web viewer ?  
defaultOptions.renderer.kind += OptionKind.PREFERENCE;
} else if (PDFJSDev.test("CHROME")) {
  defaultOptions.disableTelemetry = {
    
    value: false,
    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
  };
  defaultOptions.sandboxBundleSrc = {
    
    value: "../build/pdf.sandbox.js",
    kind: OptionKind.VIEWER,
  };
}
const userOptions = Object.create(null);
class AppOptions {
  constructor() {
    throw new Error("Cannot initialize AppOptions.");
  }
  static get(name) {
    const userOption = userOptions[name];
    if (userOption !== undefined) {
      return userOption;
    }
    const defaultOption = defaultOptions[name];
    if (defaultOption !== undefined) {
      return defaultOption.compatibility ?? defaultOption.value;
    }
    return undefined;
  }
  static getAll(kind = null) {