  - 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 ?  
value: false,
    kind: OptionKind.API + OptionKind.PREFERENCE,
  },
  disableStream: {
    
    value: false,
    kind: OptionKind.API + OptionKind.PREFERENCE,
  },
  docBaseUrl: {
    
    value: "",
    kind: OptionKind.API,
  },
  enableXfa: {
    
    value:
      typeof PDFJSDev === "undefined" ||
      PDFJSDev.test("!PRODUCTION || TESTING"),
    kind: OptionKind.API + OptionKind.PREFERENCE,
  },
  fontExtraProperties: {
    
    value: false,
    kind: OptionKind.API,
  },
  isEvalSupported: {
    
    value: true,
    kind: OptionKind.API,