Attach (recommended) or Link to PDF file here:
http://education.ohio.gov/getattachment/Topics/Special-Education/Preschool-Special-Education/ETR-Preschool-Planning-Form.pdf.aspx

- Web browser and its version: Firefox 89.0.1
- Operating system and its version: Windows 10 10.0.19043.1052
- PDF.js version: commit 5d251a3a3e7bfaa8fbfa07f0b7f9901eb3f999d9
- Is a browser extension: No

Steps to reproduce the problem:
1. Enable XFA support
2. Open form

What is the expected behavior? (add screenshot)
Shapes stay inside table cells
![image](https://user-images.githubusercontent.com/7104454/122572782-1252a580-d01c-11eb-9d0f-5fed46d6f2fe.png)

What went wrong? (add screenshot)
Shapes fall outside cells (among other issues)
![image](https://user-images.githubusercontent.com/7104454/122572885-2d251a00-d01c-11eb-8863-fa3b9969f0ea.png)

const edges = this.edge.children.slice();
    if (edges.length < 4) {
      const defaultEdge = edges[edges.length - 1] || new Edge({});
      for (let i = edges.length; i < 4; i++) {
        edges.push(defaultEdge);
      }
    }
    const edgeStyles = edges.map(node => {
      const style = node[$toStyle]();
      style.color = style.color || "#000000";
      return style;
    });
    const widths = edges.map(edge => edge.thickness);
    const insets = [0, 0, 0, 0];
    if (this.margin) {
      insets[0] = this.margin.topInset;
      insets[1] = this.margin.rightInset;
      insets[2] = this.margin.bottomInset;
      insets[3] = this.margin.leftInset;
    }
    this[$extra] = { widths, insets };
    
    const style = Object.create(null);
    if (this.margin) {
      Object.assign(style, this.margin[$toStyle]());
    }
    if (this.fill && this.fill.presence === "visible") {