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

Source/core/css/parser/CSSPropertyParser.cpp

 /*
  * Copyright (C) 2003 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Nicholas Shanks <webkit@nickshanks.com>
  * Copyright (C) 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2012 Adobe Systems Incorporated. All rights reserved.
  * Copyright (C) 2012 Intel Corporation. All rights reserved.
  *
@@ skipping 3697 matching lines @@
         }
         currentCol = lookAheadCol;
     }
 
     m_valueList->next();
     return true;
 }
 
 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;
 
     while (m_valueList->current()) {
         if (!parseGridTemplateAreasRow(gridAreaMap, rowCount, columnCount))
             return nullptr;
         ++rowCount;
     }
 
@@ skipping 4677 matching lines @@
         }
     }
 
     if (!list->length())
         return nullptr;
 
     return list.release();
 }
 
 } // namespace blink