[CSS Grid Layout] Disallow using <ident> and function names as <custom-ident>

LayoutTests/fast/css-grid-layout/grid-element-repeat-get-set.html

Index: LayoutTests/fast/css-grid-layout/grid-element-repeat-get-set.html
diff --git a/LayoutTests/fast/css-grid-layout/grid-element-repeat-get-set.html b/LayoutTests/fast/css-grid-layout/grid-element-repeat-get-set.html
index 2b4c5f6143a26908ee1beb83090023d99a636460..4222f2900f5501e42344f83801caff9b8e6f90cf 100644
--- a/LayoutTests/fast/css-grid-layout/grid-element-repeat-get-set.html
+++ b/LayoutTests/fast/css-grid-layout/grid-element-repeat-get-set.html
@@ -120,6 +120,7 @@ if (window.testRunner)
     function testInvalidSyntax(gridColumn) {
         element = document.createElement("div");
         document.body.appendChild(element);
+        element.style.display = "grid";
         element.style.gridTemplateColumns = gridColumn;
         shouldBeEqualToString("window.getComputedStyle(element, '').getPropertyValue('grid-template-columns')", "none");
         document.body.removeChild(element);
@@ -130,6 +131,12 @@ if (window.testRunner)
     testInvalidSyntax("repeat(3 , ,)");
     testInvalidSyntax("repeat(0, 15px)");
     testInvalidSyntax("repeat(-1, auto)");
+    testInvalidSyntax("repeat(1, (auto) 10px)");
+    testInvalidSyntax("repeat(1, (start auto) 10px)");
+    testInvalidSyntax("repeat(1, 10px (minmax))");
+    testInvalidSyntax("repeat(1, 10px (minmax end))");
+    testInvalidSyntax("repeat(1, 2em (subgrid) 10px)");
+    testInvalidSyntax("repeat(1, 2em (middle subgrid) 10px)");
     // Nesting is no allowed.
     testInvalidSyntax("repeat(2, repeat(1, auto))");
 </script>