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.
ctx.clip = function ctxRotate(rule) {
    destCtx.clip(rule);
    this.__originalClip(rule);
  };
  ctx.moveTo = function (x, y) {
    destCtx.moveTo(x, y);
    this.__originalMoveTo(x, y);
  };
  ctx.lineTo = function (x, y) {
    destCtx.lineTo(x, y);
    this.__originalLineTo(x, y);
  };
  ctx.bezierCurveTo = function (cp1x, cp1y, cp2x, cp2y, x, y) {
    destCtx.bezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y);
    this.__originalBezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y);
  };
  ctx.rect = function (x, y, width, height) {
    destCtx.rect(x, y, width, height);
    this.__originalRect(x, y, width, height);
  };
  ctx.closePath = function () {
    destCtx.closePath();
    this.__originalClosePath();
  };
  ctx.beginPath = function () {
    destCtx.beginPath();
    this.__originalBeginPath();
  };
}
function addContextCurrentTransform(ctx) {