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

Source/core/svg/SVGFilterElement.h

Index: Source/core/svg/SVGFilterElement.h
diff --git a/Source/core/svg/SVGFilterElement.h b/Source/core/svg/SVGFilterElement.h
index 21eb30c727caf6631c01e8e3907fccd9555d5209..beb5b1204ef07e30a2fbb7a7a845859091354499 100644
--- a/Source/core/svg/SVGFilterElement.h
+++ b/Source/core/svg/SVGFilterElement.h
@@ -46,6 +46,8 @@ public:
 
     void setFilterRes(unsigned filterResX, unsigned filterResY);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGStyledElement::accept(visitor); }
+
 private:
     SVGFilterElement(const QualifiedName&, const Handle<Document>&);