Attach (recommended) or Link to PDF file here:
[output.pdf](https://github.com/mozilla/pdf.js/files/6374987/output.pdf)

Configuration:
- Web browser and its version: Firefox 88.0
- Operating system and its version: macOS Big Sur 11.2.3 (20D91)
- PDF.js version: 2.8.243
- Is a browser extension: no/Firefox built-in

Steps to reproduce the problem:
1.  add Ink-Annotations to a pdf (i use https://github.com/highkite/pdfAnnotate, Annotations with appearance streams are shown correctly)
2. open output file in firefox

What is the expected behavior? 
The annotations should be visible.
![Bildschirmfoto 2021-04-26 um 09 15 48](https://user-images.githubusercontent.com/33630884/116043809-6a020f80-a670-11eb-973c-6f2df3dae532.png)

What went wrong? 
The annotations are added to the dom but invisible.
![Bildschirmfoto 2021-04-26 um 09 18 26](https://user-images.githubusercontent.com/33630884/116043867-7e460c80-a670-11eb-964d-0cc2c6dbfb61.png)

Tested successfull with FoxitReader, AcrobatReader, Chrome and Safari.
line = font.encodeString(line).join("");
    const glyphs = font.charsToGlyphs(line);
    if (glyphs.length <= 1) {
      
      return [line];
    }
    const positions = font.getCharPositions(line);
    const scale = fontSize / 1000;
    const chunks = [];
    let lastSpacePosInStringStart = -1,
      lastSpacePosInStringEnd = -1,
      lastSpacePos = -1,
      startChunk = 0,
      currentWidth = 0;
    for (let i = 0, ii = glyphs.length; i < ii; i++) {
      const [start, end] = positions[i];
      const glyph = glyphs[i];
      const glyphWidth = glyph.width * scale;
      if (glyph.unicode === " ") {
        if (currentWidth + glyphWidth > width) {
          
          chunks.push(line.substring(startChunk, start));
          startChunk = start;
          currentWidth = glyphWidth;
          lastSpacePosInStringStart = -1;
          lastSpacePos = -1;
        } else {
          currentWidth += glyphWidth;