Attach (recommended) or Link to PDF file here:
[Erstattung von Arbeitgeberaufwendungen nach __ 56 Abs. 1 und 57, 58 Infektionsschutzgesetz - Antrag(1).pdf](https://github.com/mozilla/pdf.js/files/6009589/Erstattung.von.Arbeitgeberaufwendungen.nach.__.56.Abs.1.und.57.58.Infektionsschutzgesetz.-.Antrag.1.pdf)

Also available at: [formularserver.bayern.de](https://formularserver.bayern.de/intelliform/forms/stmi+regierungen/rof/b5/55.2/rof_55.2-086/index)

Configuration:
- Web browser and its version: FF 85.0.2 and FF 86.0b9
- Operating system and its version: Win 10
- PDF.js version: 
FF 85.0.2:
const pdfjsVersion = '2.7.345';
const pdfjsBuild = 'b194c820b';

FF 86.0b9:
const pdfjsVersion = '2.7.510';
const pdfjsBuild = '631bada0d';

- Is a browser extension:
no
Steps to reproduce the problem:
1. load pdf document

What is the expected behavior? (add screenshot)
This is with latest Chrome:
![grafik](https://user-images.githubusercontent.com/584660/108499622-e2360880-72ae-11eb-82a7-b181619ff079.png)


What went wrong? (add screenshot)
The checkboxes for e.g. "Geschlecht" are black and you cannot see which one is checked. But this is true for every checkbox in that document.
![grafik](https://user-images.githubusercontent.com/584660/108499753-14e00100-72af-11eb-89d3-1f5ca652e058.png)

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

title.dir = this.titleObj.dir;
    title.textContent = this.titleObj.str;
    popup.appendChild(title);
    
    
    
    const dateObject = PDFDateString.toDateObject(this.modificationDate);
    if (dateObject) {
      const modificationDate = document.createElement("span");
      modificationDate.textContent = "{{date}}, {{time}}";
      modificationDate.dataset.l10nId = "annotation_date_string";
      modificationDate.dataset.l10nArgs = JSON.stringify({
        date: dateObject.toLocaleDateString(),
        time: dateObject.toLocaleTimeString(),
      });
      popup.appendChild(modificationDate);
    }
    const contents = this._formatContents(this.contentsObj);
    popup.appendChild(contents);
    if (!Array.isArray(this.trigger)) {
      this.trigger = [this.trigger];
    }
    
    for (const element of this.trigger) {
      element.addEventListener("click", this._toggle.bind(this));
      element.addEventListener("mouseover", this._show.bind(this, false));
      element.addEventListener("mouseout", this._hide.bind(this, false));
    }
    popup.addEventListener("click", this._hide.bind(this, true));
    wrapper.appendChild(popup);