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
ctx.globalAlpha = this.current.fillAlpha;
    },
    closeStroke: function CanvasGraphics_closeStroke() {
      this.closePath();
      this.stroke();
    },
    fill: function CanvasGraphics_fill(consumePath) {
      consumePath = typeof consumePath !== "undefined" ? consumePath : true;
      const ctx = this.ctx;
      const fillColor = this.current.fillColor;
      const isPatternFill = this.current.patternFill;
      let needRestore = false;
      if (isPatternFill) {
        ctx.save();
        if (this.baseTransform) {
          ctx.setTransform.apply(ctx, this.baseTransform);
        }
        ctx.fillStyle = fillColor.getPattern(ctx, this);
        needRestore = true;
      }
      if (this.contentVisible) {
        if (this.pendingEOFill) {
          ctx.fill("evenodd");
          this.pendingEOFill = false;
        } else {
          ctx.fill();
        }
      }
      if (needRestore) {