Implement DOMQuad of geometry interfaces.

Source/core/dom/DOMPoint.h

Index: Source/core/dom/DOMPoint.h
diff --git a/Source/core/dom/DOMPoint.h b/Source/core/dom/DOMPoint.h
index c966b20058771db169e62827ce14142de4df2ea3..2c12af2df48fb2bf6dca99be4fd0a3936eb91b88 100644
--- a/Source/core/dom/DOMPoint.h
+++ b/Source/core/dom/DOMPoint.h
@@ -11,14 +11,14 @@ namespace blink {
 
 class DOMPointInit;
 
-class DOMPoint final : public DOMPointReadOnly {
+class DOMPoint : public DOMPointReadOnly {
     DEFINE_WRAPPERTYPEINFO();
 public:
     static DOMPoint* create(const DOMPointInit&);
-    static DOMPoint* create(double x, double y, double z = 0, double w = 1);
+    static DOMPoint* create(double x = 0, double y = 0, double z = 0, double w = 1);
 
-    void setX(double x) { m_x = x; }
-    void setY(double y) { m_y = y; }
+    virtual void setX(double x) { m_x = x; }
+    virtual void setY(double y) { m_y = y; }
     void setZ(double z) { m_z = z; }
     void setW(double w) { m_w = w; }