  - 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 ?  
* It does this by creating overlay divs over the PDF's text. These divs
 * contain text that matches the PDF text they are overlaying.
 */
class TextLayerBuilder {
  constructor({
    textLayerDiv,
    eventBus,
    pageIndex,
    viewport,
    highlighter = null,
    enhanceTextSelection = false,
  }) {
    this.textLayerDiv = textLayerDiv;
    this.eventBus = eventBus;
    this.textContent = null;
    this.textContentItemsStr = [];
    this.textContentStream = null;
    this.renderingDone = false;
    this.pageNumber = pageIndex + 1;
    this.viewport = viewport;
    this.textDivs = [];
    this.textLayerRenderTask = null;
    this.highlighter = highlighter;
    this.enhanceTextSelection = enhanceTextSelection;
    this._bindMouse();
  }
  /**
   * @private
   */
  _finishRendering() {