[CSS Grid Layout] grid-template-areas should accept none value

Source/core/css/parser/CSSPropertyParser.cpp

Index: Source/core/css/parser/CSSPropertyParser.cpp
diff --git a/Source/core/css/parser/CSSPropertyParser.cpp b/Source/core/css/parser/CSSPropertyParser.cpp
index 17a2b6113f22a83f9cdab3c68c21d7250b6f3ed8..b09d42d932671ea83c2b3d8e3715f6bb1d1e58fa 100644
--- a/Source/core/css/parser/CSSPropertyParser.cpp
+++ b/Source/core/css/parser/CSSPropertyParser.cpp
@@ -3715,6 +3715,11 @@ bool CSSPropertyParser::parseGridTemplateAreasRow(NamedGridAreaMap& gridAreaMap,
 
 PassRefPtrWillBeRawPtr<CSSValue> CSSPropertyParser::parseGridTemplateAreas()
 {
+    if (m_valueList->current() && m_valueList->current()->id == CSSValueNone) {
+        m_valueList->next();
+        return cssValuePool().createIdentifierValue(CSSValueNone);
+    }
+
     NamedGridAreaMap gridAreaMap;
     size_t rowCount = 0;
     size_t columnCount = 0;