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

Source/core/svg/SVGFELightElement.h

Index: Source/core/svg/SVGFELightElement.h
diff --git a/Source/core/svg/SVGFELightElement.h b/Source/core/svg/SVGFELightElement.h
index 1b9f25a059c23b8bd6c8a627d9f3fe23c5b5ec72..18798486c0aa5cc27c30aaf2c0d2ac9ad782cfc5 100644
--- a/Source/core/svg/SVGFELightElement.h
+++ b/Source/core/svg/SVGFELightElement.h
@@ -35,6 +35,8 @@ public:
     static SVGFELightElement* findLightElement(const SVGElement*);
     static PassRefPtr<LightSource> findLightSource(const SVGElement*);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGElement::accept(visitor); }
+
 protected:
     SVGFELightElement(const QualifiedName&, const Handle<Document>&);