Introduce a SVGUnknownElement class for unknown SVG elements

Source/core/svg/SVGSymbolElement.h

 /*
  * Copyright (C) 2004, 2005 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006 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 27 matching lines @@
 
 private:
     SVGSymbolElement(const QualifiedName&, Document*);
 
     virtual bool supportsFocus() const OVERRIDE { return hasFocusEventListeners(); }
 
     bool isSupportedAttribute(const QualifiedName&);
     virtual void parseAttribute(const QualifiedName&, const AtomicString&) OVERRIDE;
     virtual void svgAttributeChanged(const QualifiedName&);
 
-    virtual bool rendererIsNeeded(const NodeRenderingContext& context) OVERRIDE { return rendererIsNeededInternal(context); }
     virtual RenderObject* createRenderer(RenderStyle*);
 
     virtual bool selfHasRelativeLengths() const;
 
     BEGIN_DECLARE_ANIMATED_PROPERTIES(SVGSymbolElement)
         DECLARE_ANIMATED_BOOLEAN(ExternalResourcesRequired, externalResourcesRequired)
         DECLARE_ANIMATED_RECT(ViewBox, viewBox)
         DECLARE_ANIMATED_PRESERVEASPECTRATIO(PreserveAspectRatio, preserveAspectRatio)
     END_DECLARE_ANIMATED_PROPERTIES
 };
 
 } // namespace WebCore
 
 #endif