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

Source/core/svg/SVGFEDistantLightElement.h

Index: Source/core/svg/SVGFEDistantLightElement.h
diff --git a/Source/core/svg/SVGFEDistantLightElement.h b/Source/core/svg/SVGFEDistantLightElement.h
index 0141fbee2b734224ff7e7d038fc05da3b91b9822..5d2653e5184cbb62f3fce8334f5f46f2f611a3ee 100644
--- a/Source/core/svg/SVGFEDistantLightElement.h
+++ b/Source/core/svg/SVGFEDistantLightElement.h
@@ -29,6 +29,8 @@ class SVGFEDistantLightElement : public SVGFELightElement {
 public:
     static PassRefPtr<SVGFEDistantLightElement> create(const QualifiedName&, const Handle<Document>&);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGFELightElement::accept(visitor); }
+
 private:
     SVGFEDistantLightElement(const QualifiedName&, const Handle<Document>&);