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

Source/core/svg/SVGFESpotLightElement.h

Index: Source/core/svg/SVGFESpotLightElement.h
diff --git a/Source/core/svg/SVGFESpotLightElement.h b/Source/core/svg/SVGFESpotLightElement.h
index 28860fbfc955545c33f67ea39af50fd01fd4cc5b..1309d149c4d28007e779f3c037eaafd474adeb99 100644
--- a/Source/core/svg/SVGFESpotLightElement.h
+++ b/Source/core/svg/SVGFESpotLightElement.h
@@ -29,6 +29,8 @@ class SVGFESpotLightElement : public SVGFELightElement {
 public:
     static PassRefPtr<SVGFESpotLightElement> create(const QualifiedName&, const Handle<Document>&);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGFELightElement::accept(visitor); }
+
 private:
     SVGFESpotLightElement(const QualifiedName&, const Handle<Document>&);