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

Source/core/svg/SVGFEFloodElement.h

Index: Source/core/svg/SVGFEFloodElement.h
diff --git a/Source/core/svg/SVGFEFloodElement.h b/Source/core/svg/SVGFEFloodElement.h
index 4d8135141609685a0c66619e50e4a5eb5a24c499..cda4867d5b33ea1c3da7c22796918dff23985280 100644
--- a/Source/core/svg/SVGFEFloodElement.h
+++ b/Source/core/svg/SVGFEFloodElement.h
@@ -31,6 +31,8 @@ class SVGFEFloodElement : public SVGFilterPrimitiveStandardAttributes {
 public:
     static PassRefPtr<SVGFEFloodElement> create(const QualifiedName&, const Handle<Document>&);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGFilterPrimitiveStandardAttributes::accept(visitor); }
+
 private:
     SVGFEFloodElement(const QualifiedName&, const Handle<Document>&);