Store marker identifiers as AtomicString

Source/core/rendering/style/SVGRenderStyleDefs.h

 /*
     Copyright (C) 2004, 2005, 2007 Nikolas Zimmermann <zimmermann@kde.org>
                   2004, 2005 Rob Buis <buis@kde.org>
     Copyright (C) Research In Motion Limited 2010. All rights reserved.
 
     Based on khtml code by:
     Copyright (C) 2000-2003 Lars Knoll (knoll@kde.org)
               (C) 2000 Antti Koivisto (koivisto@kde.org)
               (C) 2000-2003 Dirk Mueller (mueller@kde.org)
               (C) 2002-2003 Apple Computer, Inc.
@@ skipping 239 matching lines @@
     public:
         static PassRefPtr<StyleInheritedResourceData> create() { return adoptRef(new StyleInheritedResourceData); }
         PassRefPtr<StyleInheritedResourceData> copy() const { return adoptRef(new StyleInheritedResourceData(*this)); }
 
         bool operator==(const StyleInheritedResourceData&) const;
         bool operator!=(const StyleInheritedResourceData& other) const
         {
             return !(*this == other);
         }
 
-        String markerStart;
-        String markerMid;
-        String markerEnd;
+        AtomicString markerStart;
+        AtomicString markerMid;
+        AtomicString markerEnd;
 
     private:
         StyleInheritedResourceData();
         StyleInheritedResourceData(const StyleInheritedResourceData&);
     };
 
 } // namespace WebCore
 
 #endif // SVGRenderStyleDefs_h