Introduce a SVGUnknownElement class for unknown SVG elements

Source/core/svg/SVGMPathElement.h

 /*
  * Copyright (C) 2007 Eric Seidel <eric@webkit.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,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 36 matching lines @@
 
     void buildPendingResource();
     void clearResourceReferences();
     virtual InsertionNotificationRequest insertedInto(ContainerNode*) OVERRIDE;
     void removedFrom(ContainerNode*);
 
     bool isSupportedAttribute(const QualifiedName&);
     virtual void parseAttribute(const QualifiedName&, const AtomicString&) OVERRIDE;
     virtual void svgAttributeChanged(const QualifiedName&) OVERRIDE;
 
+    virtual bool rendererIsNeeded(const NodeRenderingContext&) OVERRIDE { return false; }
     void notifyParentOfPathChange(ContainerNode*);
 
     BEGIN_DECLARE_ANIMATED_PROPERTIES(SVGMPathElement)
         DECLARE_ANIMATED_STRING(Href, href)
         DECLARE_ANIMATED_BOOLEAN(ExternalResourcesRequired, externalResourcesRequired)
     END_DECLARE_ANIMATED_PROPERTIES
 };
 
 } // namespace WebCore
 
 #endif // SVGMPathElement_h