Attach (recommended) or Link to PDF file here:

Configuration:
- Web browser and its version: Firefox 88.0.1
- Operating system and its version: Windows 10.0.19043.985]
- PDF.js version: (commit 706c27b9d4b3b9ff6fc3de82bcf71a0610604a1c) (also tested pr/13473 at 296bbdc4)
- Is a browser extension: N/A

Steps to reproduce the problem:
1. Enable experimental XFA
2. Open PDF
[dir2020-02_form.pdf](https://github.com/mozilla/pdf.js/files/6571084/dir2020-02_form.pdf)

What is the expected behavior? (add screenshot)
Margins of `subforms` (e.g. *General_Election_Information*, *General_Information_Other*) are honored.
![image](https://user-images.githubusercontent.com/7104454/120212605-32066300-c200-11eb-9c66-f2d05c9451ec.png)
What went wrong? (add screenshot)
Margins are not honored. 
![image](https://user-images.githubusercontent.com/7104454/120212535-1ac77580-c200-11eb-8332-9924602ef991.png)

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):

html.appendChild(document.createTextNode(child.value));
        continue;
      }
      const childHtml = document.createElement(name);
      html.appendChild(childHtml);
      if (child.attributes) {
        this.setAttributes(childHtml, child, storage, intent);
      }
      if (child.children && child.children.length > 0) {
        stack.push([child, -1, childHtml]);
      } else if (child.value) {
        childHtml.appendChild(document.createTextNode(child.value));
      }
    }
  }
  /**
   * Update the xfa layer.
   *
   * @public
   * @param {XfaLayerParameters} parameters
   * @memberof XfaLayer
   */
  static update(parameters) {
    const transform = `matrix(${parameters.viewport.transform.join(",")})`;
    parameters.div.style.transform = transform;
    parameters.div.hidden = false;
  }
}
export { XfaLayer };