Implement DOMPoint of geometry interfaces.

Source/core/dom/DOMPoint.idl

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// FIXME: Blink doesn't currently support dictionary definitions.
+// For now, we can use Dictionary interface. See http://crbug.com/321462.
+// dictionary DOMPointInit {
+//     unrestricted double x = 0;
+//     unrestricted double y = 0;
+//     unrestricted double z = 0;
+//     unrestricted double w = 1;
+// };
+
+[
+    Constructor(optional Dictionary point),
+    Constructor(unrestricted double x, unrestricted double y,
+                optional unrestricted double z = 0, optional unrestricted double w = 1),
+    RuntimeEnabled=GeometryInterfaces,
+] interface DOMPoint : DOMPointReadOnly {
+    attribute unrestricted double x;
+    attribute unrestricted double y;
+    attribute unrestricted double z;
+    attribute unrestricted double w;
+};