  - 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 ?  
const SCALE = 1.0;
const container = document.getElementById("pageContainer");
const eventBus = new pdfjsViewer.EventBus();
const loadingTask = pdfjsLib.getDocument({
  url: DEFAULT_URL,
  cMapUrl: CMAP_URL,
  cMapPacked: CMAP_PACKED,
});
loadingTask.promise.then(function (pdfDocument) {
  
  return pdfDocument.getPage(PAGE_TO_VIEW).then(function (pdfPage) {
    
    const pdfPageView = new pdfjsViewer.PDFPageView({
      container,
      id: PAGE_TO_VIEW,
      scale: SCALE,
      defaultViewport: pdfPage.getViewport({ scale: SCALE }),
      eventBus,
      
      textLayerFactory: new pdfjsViewer.DefaultTextLayerFactory(),
      annotationLayerFactory: new pdfjsViewer.DefaultAnnotationLayerFactory(),
      xfaLayerFactory: new pdfjsViewer.DefaultXfaLayerFactory(),
      structTreeLayerFactory: new pdfjsViewer.DefaultStructTreeLayerFactory(),
    });
    
    pdfPageView.setPdfPage(pdfPage);
    return pdfPageView.draw();
  });
});