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

Source/core/svg/SVGFEFuncGElement.h

Index: Source/core/svg/SVGFEFuncGElement.h
diff --git a/Source/core/svg/SVGFEFuncGElement.h b/Source/core/svg/SVGFEFuncGElement.h
index 600fc6c05cffb5f6337fdb6773e7bcbdae67fb4a..6112a3cb7219d20349cba51ce21abefb0143f692 100644
--- a/Source/core/svg/SVGFEFuncGElement.h
+++ b/Source/core/svg/SVGFEFuncGElement.h
@@ -30,6 +30,8 @@ class SVGFEFuncGElement : public SVGComponentTransferFunctionElement {
 public:
     static PassRefPtr<SVGFEFuncGElement> create(const QualifiedName&, const Handle<Document>&);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGComponentTransferFunctionElement::accept(visitor); }
+
 private:
     SVGFEFuncGElement(const QualifiedName&, const Handle<Document>&);
 };