Updated SVGListPropertyHelper as per SVG2 Spec

Source/core/svg/SVGPathSeg.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2008 Rob Buis <buis@kde.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 134 matching lines @@
 
         m_ownerList = ownerList;
     }
 
     void setContextElement(SVGElement* contextElement)
     {
         m_contextElement = contextElement;
     }
 
     static PassRefPtrWillBeRawPtr<SVGPathSeg> create() { ASSERT_NOT_REACHED(); return nullptr; }
-    PassRefPtrWillBeRawPtr<SVGPathSeg> clone() { ASSERT_NOT_REACHED(); return nullptr; }
+    virtual PassRefPtrWillBeRawPtr<SVGPathSeg> clone() = 0;
 
     DECLARE_VIRTUAL_TRACE();
 
 protected:
     void commitChange();
 
 private:
     RawPtrWillBeMember<SVGPropertyBase> m_ownerList;
     RawPtrWillBeMember<SVGElement> m_contextElement;
 };
@@ skipping 23 matching lines @@
     }
 
 private:
     float m_x;
     float m_y;
 };
 
 } // namespace blink
 
 #endif // SVGPathSeg_h