Add support for SVG Clip paths in HTML

Source/core/svg/SVGClipPathElement.h

Index: Source/core/svg/SVGClipPathElement.h
diff --git a/Source/core/svg/SVGClipPathElement.h b/Source/core/svg/SVGClipPathElement.h
index 71f2f19a8458c9a5af408b4872fe45c35dd078ac..91a2d4d0bf5984683012823c22df766c88119156 100644
--- a/Source/core/svg/SVGClipPathElement.h
+++ b/Source/core/svg/SVGClipPathElement.h
@@ -34,10 +34,15 @@ class RenderObject;
 class SVGClipPathElement FINAL : public SVGGraphicsElement {
 public:
     DECLARE_NODE_FACTORY(SVGClipPathElement);
+    virtual void trace(Visitor*) OVERRIDE;
+
     SVGAnimatedEnumeration<SVGUnitTypes::SVGUnitType>* clipPathUnits() { return m_clipPathUnits.get(); }
 
     virtual bool supportsFocus() const OVERRIDE { return false; }
 
+    void addClient(Node*);
+    void removeClient(Node*);
+
 private:
     explicit SVGClipPathElement(Document&);
 
@@ -51,6 +56,8 @@ private:
     virtual RenderObject* createRenderer(RenderStyle*) OVERRIDE;
 
     RefPtr<SVGAnimatedEnumeration<SVGUnitTypes::SVGUnitType> > m_clipPathUnits;
+
+    HashSet<RefPtr<Node> > m_clientsToAdd;
 };
 
 }