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

Source/core/svg/SVGFEGaussianBlurElement.h

Index: Source/core/svg/SVGFEGaussianBlurElement.h
diff --git a/Source/core/svg/SVGFEGaussianBlurElement.h b/Source/core/svg/SVGFEGaussianBlurElement.h
index 9eb9935ea73a8d5ef362dc1fc9ed9cdbfaa16760..4c8f4bb77c9b77d9e53b099542b1a7e8411491ca 100644
--- a/Source/core/svg/SVGFEGaussianBlurElement.h
+++ b/Source/core/svg/SVGFEGaussianBlurElement.h
@@ -34,6 +34,8 @@ public:
 
     void setStdDeviation(float stdDeviationX, float stdDeviationY);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGFilterPrimitiveStandardAttributes::accept(visitor); }
+
 private:
     SVGFEGaussianBlurElement(const QualifiedName&, const Handle<Document>&);