Fix handling of 'inherit' and 'initial' for grid lines

LayoutTests/fast/css-grid-layout/grid-item-column-row-get-set.html

Index: LayoutTests/fast/css-grid-layout/grid-item-column-row-get-set.html
diff --git a/LayoutTests/fast/css-grid-layout/grid-item-column-row-get-set.html b/LayoutTests/fast/css-grid-layout/grid-item-column-row-get-set.html
index d607cc28db4ab6524f82ee41c53ea7d6c20c45ae..a35d041b474affbb60676905e6b43d8e6dcae7a2 100755
--- a/LayoutTests/fast/css-grid-layout/grid-item-column-row-get-set.html
+++ b/LayoutTests/fast/css-grid-layout/grid-item-column-row-get-set.html
@@ -128,6 +128,16 @@ if (window.testRunner)
     shouldBe("getComputedStyle(element, '').getPropertyValue('-webkit-grid-after')", "'auto'");
 
     debug("");
+    debug("Test getting and setting 'initial' grid-column and grid-row through JS");
+    testColumnRowInitialJSParsing();
+
+    debug("");
+    debug("Test getting and setting 'inherit' grid-column and grid-row through JS");
+    testColumnRowInheritJSParsing("1 / auto", "inherit");
+    testColumnRowInheritJSParsing("inherit", "1 / auto");
+    testColumnRowInheritJSParsing("inherit", "inherit");
+
+    debug("");
     debug("Test getting and setting invalid grid-column and grid-row through JS");
     testColumnRowInvalidJSParsing("4 5", "5 8");
     testColumnRowInvalidJSParsing("4 /", "5 /");