This is a regression from #12864. The underscore is now too thin when the document is zoomed in.

URL: https://github.com/mozilla/pdf.js/files/2321540/issue6127.pdf
PDF.js 2.7.526: https://i.imgur.com/T4mIpct.png
PDF.js 2.7.510: https://i.imgur.com/nbwEpGT.png
Adobe Acrobat Reader DC 2020.013.20074: https://i.imgur.com/wDFBf3R.png

The screenshots were taken at 400% zoom.
this.pendingEOFill = true;
    this.fillStroke();
  }
  closeFillStroke() {
    this.closePath();
    this.fillStroke();
  }
  closeEOFillStroke() {
    this.pendingEOFill = true;
    this.closePath();
    this.fillStroke();
  }
  endPath() {
    this.consumePath();
  }
  
  clip() {
    this.pendingClip = NORMAL_CLIP;
  }
  eoClip() {
    this.pendingClip = EO_CLIP;
  }
  
  beginText() {
    this.current.textMatrix = IDENTITY_MATRIX;
    this.current.textMatrixScale = 1;
    this.current.x = this.current.lineX = 0;
    this.current.y = this.current.lineY = 0;
  }
  endText() {