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

Source/core/css/CSSComputedStyleDeclaration.cpp

Index: Source/core/css/CSSComputedStyleDeclaration.cpp
diff --git a/Source/core/css/CSSComputedStyleDeclaration.cpp b/Source/core/css/CSSComputedStyleDeclaration.cpp
index 2888b8d003b6e54ddb19045b1dff264dedf3b458..16a1cf1391b7f6ca062efce639cc6458621f38bd 100644
--- a/Source/core/css/CSSComputedStyleDeclaration.cpp
+++ b/Source/core/css/CSSComputedStyleDeclaration.cpp
@@ -1914,13 +1914,13 @@ PassRefPtr<CSSValue> CSSComputedStyleDeclaration::getPropertyCSSValue(CSSPropert
             return valueForGridTrackList(style->gridRows(), style.get(), m_node->document()->renderView());
 
         case CSSPropertyWebkitGridStart:
-            return valueForGridPosition(style->gridItemStart());
+            return valueForGridPosition(style->gridStart());
         case CSSPropertyWebkitGridEnd:
-            return valueForGridPosition(style->gridItemEnd());
+            return valueForGridPosition(style->gridEnd());
         case CSSPropertyWebkitGridBefore:
-            return valueForGridPosition(style->gridItemBefore());
+            return valueForGridPosition(style->gridBefore());
         case CSSPropertyWebkitGridAfter:
-            return valueForGridPosition(style->gridItemAfter());
+            return valueForGridPosition(style->gridAfter());
         case CSSPropertyWebkitGridColumn:
             return getCSSPropertyValuesForGridShorthand(webkitGridColumnShorthand());
         case CSSPropertyWebkitGridRow: