  - 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 ?  
});
    div.addEventListener("mouseup", () => {
      if (this.enhanceTextSelection && this.textLayerRenderTask) {
        if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) {
          expandDivsTimer = setTimeout(() => {
            if (this.textLayerRenderTask) {
              this.textLayerRenderTask.expandTextDivs(false);
            }
            expandDivsTimer = null;
          }, EXPAND_DIVS_TIMEOUT);
        } else {
          this.textLayerRenderTask.expandTextDivs(false);
        }
        return;
      }
      const end = div.querySelector(".endOfContent");
      if (!end) {
        return;
      }
      if (typeof PDFJSDev === "undefined" || !PDFJSDev.test("MOZCENTRAL")) {
        end.style.top = "";
      }
      end.classList.remove("active");
    });
  }
}
/**
 * @implements IPDFTextLayerFactory
 */
class DefaultTextLayerFactory {