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

Source/core/svg/SVGGlyphElement.h

Index: Source/core/svg/SVGGlyphElement.h
diff --git a/Source/core/svg/SVGGlyphElement.h b/Source/core/svg/SVGGlyphElement.h
index 7742cd83f250c1047da06e2a0962e73c0d2f0403..76954f1522f20459fb8c7ff575ba23b3999f4475 100644
--- a/Source/core/svg/SVGGlyphElement.h
+++ b/Source/core/svg/SVGGlyphElement.h
@@ -43,6 +43,8 @@ public:
     // Helper function shared between SVGGlyphElement & SVGMissingGlyphElement
     static SVGGlyph buildGenericGlyphIdentifier(const SVGElement*);
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGStyledElement::accept(visitor); }
+
 private:
     SVGGlyphElement(const QualifiedName&, const Handle<Document>&);