Steps to reproduce the problem:
1. When using the demo application - https://mozilla.github.io/pdf.js/web/viewer.html, load  the document 5311693-1.pdf

[5311693-1.pdf](https://github.com/mozilla/pdf.js/files/5137225/5311693-1.pdf)

2. go to Page 16 of the document.

3.  The strip of  EKG data  appears to have an incorrect line width   under the  Multi-color heat rate chart.

4.  When the same document is generated by pdffactory ,  the artifact are not visible.

What is the expected behavior? (add screenshot)
![expected](https://user-images.githubusercontent.com/3577617/91461157-4622cb80-e84e-11ea-8e5d-750c7b4e64ae.PNG)

What went wrong? (add screenshot)
The EKG line strip  has an incorrect thickness.  the x-transform seems to stretch the line thickness.  See the  stri in the RED rectagngle of the attached behavior versus the GREEN rectangle

Link to a viewer (if hosted on a site other than mozilla.github.io/pdf.js or as Firefox/Chrome extension):
 https://mozilla.github.io/pdf.js/web/viewer.html
if (this.contentVisible) {
        if (typeof strokeColor === "object" && strokeColor?.getPattern) {
          
          
          ctx.save();
          
          
          
          
          const transform = ctx.mozCurrentTransform;
          const scale = Util.singularValueDecompose2dScale(transform)[0];
          ctx.strokeStyle = strokeColor.getPattern(ctx, this);
          ctx.lineWidth = Math.max(
            this.getSinglePixelWidth() * MIN_WIDTH_FACTOR,
            this.current.lineWidth * scale
          );
          ctx.stroke();
          ctx.restore();
        } else {
          
          ctx.lineWidth = Math.max(
            this.getSinglePixelWidth() * MIN_WIDTH_FACTOR,
            this.current.lineWidth
          );
          ctx.stroke();
        }
      }
      if (consumePath) {
        this.consumePath();
      }