I was wondering if WebGL is considered stable enough to be enabled by default. It makes some PDFs render much faster and it has been off by default for a while now, so we have had quite some time to test it.

If we decide to enable WebGL by default, we should not forget to update https://github.com/mozilla/pdf.js/blob/master/extensions/chromium/preferences_schema.json#L39 as well.

/cc @yurydelendik 
/cc @Snuffleupagus (because IIRC you were testing WebGL too)

c3 = tmp;
    }
    if (coords[p1 + 1] > coords[p2 + 1]) {
      tmp = p1;
      p1 = p2;
      p2 = tmp;
      tmp = c1;
      c1 = c2;
      c2 = tmp;
    }
    const x1 = (coords[p1] + context.offsetX) * context.scaleX;
    const y1 = (coords[p1 + 1] + context.offsetY) * context.scaleY;
    const x2 = (coords[p2] + context.offsetX) * context.scaleX;
    const y2 = (coords[p2 + 1] + context.offsetY) * context.scaleY;
    const x3 = (coords[p3] + context.offsetX) * context.scaleX;
    const y3 = (coords[p3 + 1] + context.offsetY) * context.scaleY;
    if (y1 >= y3) {
      return;
    }
    const c1r = colors[c1],
      c1g = colors[c1 + 1],
      c1b = colors[c1 + 2];
    const c2r = colors[c2],
      c2g = colors[c2 + 1],
      c2b = colors[c2 + 2];
    const c3r = colors[c3],
      c3g = colors[c3 + 1],
      c3b = colors[c3 + 2];
    const minY = Math.round(y1),
      maxY = Math.round(y3);