Attach (recommended) or Link to PDF file here:
[backgroundimage_not_visible_anonymisiert.pdf](https://github.com/mozilla/pdf.js/files/6544725/backgroundimage_not_visible_anonymisiert.pdf)


Configuration:
- Web browser and its version: Chrome Version 90.0.4430.212 (Offizieller Build) (x86_64)
- Operating system and its version: Windows 10, MacOs BigSur
- PDF.js version: 2.5.207
- Is a browser extension: no

Steps to reproduce the problem:
1. open the document in demo viewer.js
2.

What is the expected behavior? (add screenshot)
The backgroundimage gets rendered like in Acrobat Reader
<img width="1348" alt="Bildschirmfoto 2021-05-26 um 09 44 21" src="https://user-images.githubusercontent.com/1286150/119621970-00a82480-be07-11eb-8fed-f74ac04b840b.png">

What went wrong? (add screenshot)
Backgroundimage is not rendered only some  text
<img width="987" alt="Bildschirmfoto 2021-05-26 um 09 43 57" src="https://user-images.githubusercontent.com/1286150/119621938-fab24380-be06-11eb-92ac-4ecb2c9334b1.png">




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

const paths = this.pendingTextPaths;
      const ctx = this.ctx;
      if (paths === undefined) {
        ctx.beginPath();
        return;
      }
      ctx.save();
      ctx.beginPath();
      for (let i = 0; i < paths.length; i++) {
        const path = paths[i];
        ctx.setTransform.apply(ctx, path.transform);
        ctx.translate(path.x, path.y);
        path.addToPath(ctx, path.fontSize);
      }
      ctx.restore();
      ctx.clip();
      ctx.beginPath();
      delete this.pendingTextPaths;
    }
    setCharSpacing(spacing) {
      this.current.charSpacing = spacing;
    }
    setWordSpacing(spacing) {
      this.current.wordSpacing = spacing;
    }
    setHScale(scale) {
      this.current.textHScale = scale / 100;
    }
    setLeading(leading) {