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

Source/core/svg/SVGTitleElement.h

Index: Source/core/svg/SVGTitleElement.h
diff --git a/Source/core/svg/SVGTitleElement.h b/Source/core/svg/SVGTitleElement.h
index b1543a680248031ceb6903de7188b05cc3871fec..d184b9d4cbe2d7583ec039330fc5b84564e862e5 100644
--- a/Source/core/svg/SVGTitleElement.h
+++ b/Source/core/svg/SVGTitleElement.h
@@ -34,6 +34,8 @@ class SVGTitleElement : public SVGStyledElement,
 public:
     static PassRefPtr<SVGTitleElement> create(const QualifiedName&, const Handle<Document>&);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGStyledElement::accept(visitor); }
+
 private:
     SVGTitleElement(const QualifiedName&, const Handle<Document>&);