  - 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 ?  
) {
          clearTimeout(expandDivsTimer);
          expandDivsTimer = null;
        }
        return;
      }
      const end = div.querySelector(".endOfContent");
      if (!end) {
        return;
      }
      if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) {
        
        
        
        
        let adjustTop = evt.target !== div;
        if (typeof PDFJSDev === "undefined" || PDFJSDev.test("GENERIC")) {
          adjustTop =
            adjustTop &&
            window
              .getComputedStyle(end)
              .getPropertyValue("-moz-user-select") !== "none";
        }
        if (adjustTop) {
          const divBounds = div.getBoundingClientRect();
          const r = Math.max(0, (evt.pageY - divBounds.top) / divBounds.height);
          end.style.top = (r * 100).toFixed(2) + "%";
        }
      }
      end.classList.add("active");