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
this.ctx.save();
        
        
        this.ctx.transform.apply(
          this.ctx,
          this.compositeCtx.mozCurrentTransform
        );
      }
      this.ctx.save();
      resetCtxToDefault(this.ctx);
      if (transform) {
        this.ctx.transform.apply(this.ctx, transform);
      }
      this.ctx.transform.apply(this.ctx, viewport.transform);
      this.baseTransform = this.ctx.mozCurrentTransform.slice();
      if (this.imageLayer) {
        this.imageLayer.beginLayout();
      }
    },
    executeOperatorList: function CanvasGraphics_executeOperatorList(
      operatorList,
      executionStartIdx,
      continueCallback,
      stepper
    ) {
      const argsArray = operatorList.argsArray;
      const fnArray = operatorList.fnArray;
      let i = executionStartIdx || 0;
      const argsArrayLen = argsArray.length;