Allow determining if an SVG value has been specified

Source/core/svg/properties/NewSVGAnimatedProperty.h

 /*
  * Copyright (C) 2013 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
 G*     * Redistributions in binary form must reproduce the above
@@ skipping 49 matching lines @@
     virtual void animValDidChange();
 
     virtual bool needsSynchronizeAttribute() = 0;
     virtual void synchronizeAttribute();
 
     AnimatedPropertyType type() const
     {
         return m_type;
     }
 
-    SVGElement* contextElement()
+    SVGElement* contextElement() const
     {
         return m_contextElement;
     }
 
     const QualifiedName& attributeName() const
     {
         return m_attributeName;
     }
 
     bool isAnimating() const
     {
         return m_isAnimating;
     }
 
     bool isReadOnly() const
     {
         return m_isReadOnly;
     }
 
     void setReadOnly()
     {
         m_isReadOnly = true;
     }
 
+    bool isSpecified() const;
+
 protected:
     NewSVGAnimatedPropertyBase(AnimatedPropertyType, SVGElement*, const QualifiedName& attributeName);
     void commitChange();
 
 private:
     const AnimatedPropertyType m_type;
     bool m_isReadOnly;
     bool m_isAnimating;
 
     // This reference is kept alive from V8 wrapper
@@ skipping 209 matching lines @@
         , m_baseValueUpdated(false)
     {
     }
 
     bool m_baseValueUpdated;
 };
 
 }
 
 #endif // NewSVGAnimatedProperty_h