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):

const { attributes } = element;
    if (attributes.type === "radio") {
      
      
      attributes.name = `${attributes.name}-${intent}`;
    }
    for (const [key, value] of Object.entries(attributes)) {
      if (value === null || value === undefined || key === "fieldId") {
        continue;
      }
      if (key !== "style") {
        if (key === "textContent") {
          html.textContent = value;
        } else {
          html.setAttribute(key, value);
        }
      } else {
        Object.assign(html.style, value);
      }
    }
    
    
    if (storage && attributes.fieldId !== undefined) {
      this.setupStorage(html, attributes.fieldId, element, storage);
    }
  }
  static render(parameters) {