Actualización

app/Resources/public/assets/modernizr/feature-detects/css-calc.js

@@ -0,0 +1,12 @@
+// Method of allowing calculated values for length units, i.e. width: calc(100%-3em) http://caniuse.com/#search=calc
+// By @calvein
+
+Modernizr.addTest('csscalc', function() {
+    var prop = 'width:';
+    var value = 'calc(10px);';
+    var el = document.createElement('div');
+
+    el.style.cssText = prop + Modernizr._prefixes.join(value + prop);
+
+    return !!el.style.length;
+});