[CSS Grid Layout] the "grid-template-areas" is not identified as computable property.

Source/core/css/CSSComputedStyleDeclaration.cpp

 /*
  * Copyright (C) 2004 Zack Rusin <zack@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2011 Sencha, Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
  * License as published by the Free Software Foundation; either
@@ skipping 252 matching lines @@
     CSSPropertyFlexShrink,
     CSSPropertyFlexDirection,
     CSSPropertyFlexWrap,
     CSSPropertyJustifyContent,
     CSSPropertyWebkitFontSmoothing,
     CSSPropertyGridAutoColumns,
     CSSPropertyGridAutoFlow,
     CSSPropertyGridAutoRows,
     CSSPropertyGridColumnEnd,
     CSSPropertyGridColumnStart,
+    CSSPropertyGridTemplateAreas,
     CSSPropertyGridTemplateColumns,
     CSSPropertyGridTemplateRows,
     CSSPropertyGridRowEnd,
     CSSPropertyGridRowStart,
     CSSPropertyWebkitHighlight,
     CSSPropertyWebkitHyphenateCharacter,
     CSSPropertyWebkitLineBoxContain,
     CSSPropertyWebkitLineBreak,
     CSSPropertyWebkitLineClamp,
     CSSPropertyWebkitLocale,
@@ skipping 2759 matching lines @@
     static const CSSPropertyID propertiesAfterSlashSeperator[3] = { CSSPropertyBackgroundSize, CSSPropertyBackgroundOrigin,
                                                                     CSSPropertyBackgroundClip };
 
     RefPtrWillBeRawPtr<CSSValueList> list = CSSValueList::createSlashSeparated();
     list->append(valuesForShorthandProperty(StylePropertyShorthand(CSSPropertyBackground, propertiesBeforeSlashSeperator, WTF_ARRAY_LENGTH(propertiesBeforeSlashSeperator))));
     list->append(valuesForShorthandProperty(StylePropertyShorthand(CSSPropertyBackground, propertiesAfterSlashSeperator, WTF_ARRAY_LENGTH(propertiesAfterSlashSeperator))));
     return list.release();
 }
 
 } // namespace WebCore