Introduce a SVGUnknownElement class for unknown SVG elements

Source/core/svg/animation/SVGSMILElement.h

 /*
  * Copyright (C) 2008 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 109 matching lines @@
     virtual void setAttributeName(const QualifiedName&);
 
 private:
     void buildPendingResource();
     void clearResourceReferences();
 
     virtual void startedActiveInterval() = 0;
     void endedActiveInterval();
     virtual void updateAnimation(float percent, unsigned repeat, SVGSMILElement* resultElement) = 0;
 
+    virtual bool rendererIsNeeded(const NodeRenderingContext&) OVERRIDE { return false; }
+
     enum BeginOrEnd {
         Begin,
         End
     };
 
     SMILTime findInstanceTime(BeginOrEnd, SMILTime minimumTime, bool equalsMinimumOK) const;
     void resolveFirstInterval();
     void resolveNextInterval(bool notifyDependents);
     void resolveInterval(bool first, SMILTime& beginResult, SMILTime& endResult) const;
     SMILTime resolveActiveEnd(SMILTime resolvedBegin, SMILTime resolvedEnd) const;
@@ skipping 95 matching lines @@
 
 inline SVGSMILElement* toSVGSMILElement(Element* element)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!element || SVGSMILElement::isSMILElement(element));
     return static_cast<SVGSMILElement*>(element);
 }
 
 }
 
 #endif // SVGSMILElement_h