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

Source/core/svg/SVGFEBlendElement.h

Index: Source/core/svg/SVGFEBlendElement.h
diff --git a/Source/core/svg/SVGFEBlendElement.h b/Source/core/svg/SVGFEBlendElement.h
index 525c4a335e63329e660cffa655be93eb5c93b107..373c0791b9fcc8321a5f64eb7bc1b8897ad46689 100644
--- a/Source/core/svg/SVGFEBlendElement.h
+++ b/Source/core/svg/SVGFEBlendElement.h
@@ -73,6 +73,8 @@ class SVGFEBlendElement : public SVGFilterPrimitiveStandardAttributes {
 public:
     static PassRefPtr<SVGFEBlendElement> create(const QualifiedName&, const Handle<Document>&);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGFilterPrimitiveStandardAttributes::accept(visitor); }
+
 private:
     SVGFEBlendElement(const QualifiedName&, const Handle<Document>&);