[oilpan] Implement accept methods to trace the class hierarchy of SVGElement and all sub-classes.

Source/core/svg/SVGAnimateColorElement.h

Index: Source/core/svg/SVGAnimateColorElement.h
diff --git a/Source/core/svg/SVGAnimateColorElement.h b/Source/core/svg/SVGAnimateColorElement.h
index 42ff9976aacb7edadaa8503ae1946fd717203cca..51170269d1017405ac69e33f2aa7eed7940168d7 100644
--- a/Source/core/svg/SVGAnimateColorElement.h
+++ b/Source/core/svg/SVGAnimateColorElement.h
@@ -31,6 +31,8 @@ class SVGAnimateColorElement : public SVGAnimateElement {
 public:
     static PassRefPtr<SVGAnimateColorElement> create(const QualifiedName&, const Handle<Document>&);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGAnimateElement::accept(visitor); }
+
 private:
     SVGAnimateColorElement(const QualifiedName&, const Handle<Document>&);
     virtual void determinePropertyValueTypes(const String& from, const String& to);