[CSS Grid Layout] Implement CSSGridTemplateAreasValue::equals

Source/core/css/CSSGridTemplateAreasValue.h

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 33 matching lines @@
         return adoptRefWillBeNoop(new CSSGridTemplateAreasValue(gridAreaMap, rowCount, columnCount));
     }
     ~CSSGridTemplateAreasValue() { }
 
     String customCSSText() const;
 
     const NamedGridAreaMap& gridAreaMap() const { return m_gridAreaMap; }
     size_t rowCount() const { return m_rowCount; }
     size_t columnCount() const { return m_columnCount; }
 
+    bool equals(const CSSGridTemplateAreasValue&) const;
+
     DEFINE_INLINE_TRACE_AFTER_DISPATCH() { CSSValue::traceAfterDispatch(visitor); }
 
 private:
     CSSGridTemplateAreasValue(const NamedGridAreaMap&, size_t rowCount, size_t columnCount);
 
     NamedGridAreaMap m_gridAreaMap;
     size_t m_rowCount;
     size_t m_columnCount;
 };
 
 DEFINE_CSS_VALUE_TYPE_CASTS(CSSGridTemplateAreasValue, isGridTemplateAreasValue());
 
 } // namespace blink
 
 #endif // CSSGridTemplateAreasValue_h