  - 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 ?  
},
  sidebarViewOnLoad: {
    
    value: -1,
    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
  },
  scrollModeOnLoad: {
    
    value: -1,
    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
  },
  spreadModeOnLoad: {
    
    value: -1,
    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
  },
  textLayerMode: {
    
    value: 1,
    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
  },
  useOnlyCssZoom: {
    
    value: false,
    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,
  },
  viewerCssTheme: {
    
    value: typeof PDFJSDev !== "undefined" && PDFJSDev.test("CHROME") ? 2 : 0,
    kind: OptionKind.VIEWER + OptionKind.PREFERENCE,