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

Source/core/svg/SVGStyledLocatableElement.h

Index: Source/core/svg/SVGStyledLocatableElement.h
diff --git a/Source/core/svg/SVGStyledLocatableElement.h b/Source/core/svg/SVGStyledLocatableElement.h
index 7ce72b796e64472b369da01289690c0d7da5792a..f725c4dd29fe0272a681e687eeb925dea40919b3 100644
--- a/Source/core/svg/SVGStyledLocatableElement.h
+++ b/Source/core/svg/SVGStyledLocatableElement.h
@@ -41,6 +41,8 @@ public:
 
     virtual AffineTransform localCoordinateSpaceTransform(SVGLocatable::CTMScope mode) const { return SVGLocatable::localCoordinateSpaceTransform(mode); }
 
+    virtual void accept(Visitor* visitor) const OVERRIDE { SVGStyledElement::accept(visitor); }
+
 protected:
     SVGStyledLocatableElement(const QualifiedName&, const Handle<Document>&, ConstructionType = CreateSVGElement);