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)

ps[q + verticesPerRow + 1],
              ps[q + 1],
              ps[q + verticesPerRow],
              cs[q + verticesPerRow + 1],
              cs[q + 1],
              cs[q + verticesPerRow]
            );
          }
        }
        break;
      case "triangles":
        for (i = 0, ii = ps.length; i < ii; i += 3) {
          drawTriangle(
            data,
            context,
            ps[i],
            ps[i + 1],
            ps[i + 2],
            cs[i],
            cs[i + 1],
            cs[i + 2]
          );
        }
        break;
      default:
        throw new Error("illegal figure");
    }
  }
  
  function createMeshCanvas(