[SVG] Implement 'discard' element

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 96 matching lines @@
 
     virtual void resetAnimatedType() = 0;
     virtual void clearAnimatedType(SVGElement* targetElement) = 0;
     virtual void applyResultsToTarget() = 0;
 
     void connectConditions();
 
     void dispatchPendingEvent(SMILEventSender*);
     void dispatchRepeatEvents(unsigned);
 
+    virtual bool isSVGDiscardElement() const { return false; }
+
 protected:
     void addBeginTime(SMILTime eventTime, SMILTime endTime, SMILTimeWithOrigin::Origin = SMILTimeWithOrigin::ParserOrigin);
     void addEndTime(SMILTime eventTime, SMILTime endTime, SMILTimeWithOrigin::Origin = SMILTimeWithOrigin::ParserOrigin);
 
     void setInactive() { m_activeState = Inactive; }
 
     // Sub-classes may need to take action when the target is changed.
     virtual void setTargetElement(SVGElement*);
     virtual void setAttributeName(const QualifiedName&);
 
@@ skipping 104 matching lines @@
     mutable SMILTime m_cachedRepeatCount;
     mutable SMILTime m_cachedMin;
     mutable SMILTime m_cachedMax;
 
     friend class ConditionEventListener;
 };
 
 inline bool isSVGSMILElement(const Node& node)
 {
     return node.hasTagName(SVGNames::setTag) || node.hasTagName(SVGNames::animateTag) || node.hasTagName(SVGNames::animateMotionTag)
-        || node.hasTagName(SVGNames::animateTransformTag) || node.hasTagName(SVGNames::animateColorTag);
+        || node.hasTagName(SVGNames::animateTransformTag) || node.hasTagName(SVGNames::animateColorTag) || node.hasTagName((SVGNames::discardTag));
 }
 
 DEFINE_NODE_TYPE_CASTS_WITH_FUNCTION(SVGSMILElement);
 
 }
 
 #endif // SVGSMILElement_h