[WIP] Implement DOMPoint of geometry interface.

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,
+    // FIXME: How can we pass arguments to constructor?

[zino, 2014/07/17 13:54:30]

Question #1: How can we use multiple constructor (which has some arguments)?
I'm not sure but the arguments doesn't seem to be passed to current initialize
function.

[haraken, 2014/07/17 15:01:58]

A short answer is that constructors are not yet implemented in Blink-in-JS and
should be implemented. (I welcome your contribution :-)

initialize() in Blink-in-JS is a different thing from constructors. initialize()
is just a method to initialize members of |this| object. initialize() is called
for |this| object at the first time when any DOM attribute or DOM method of
|this| object is going to be called.

On the other hand, constructors are called when 'new DOMPoint(...)' is called. I
think we need to implement a mechanism to invoke DOMPointPrototype.new(...) when
'new DOMPoint(...)' is called. (I think we should avoid using
DOMPointPrototype.constructor(...) since "constructor" is a built-in property
and will cause unexpected conflict.)

+    // Constructor(optional Dictionary point),
+    // Constructor(unrestricted double x, unrestricted double y,
+    //             optional unrestricted double z = 0, optional unrestricted double w = 1),
+    RuntimeEnabled=GeometryInterface,
+] interface DOMPoint : DOMPointReadOnly {
+    [ImplementedInPrivateScript] inherit attribute unrestricted double x;

[haraken, 2014/07/17 15:01:58]

Before discussing Blink-in-JS, 'inherit attribute' is not supported in the IDL
compiler (because no real IDL files are using it).

Do we really need to use inherit attributes here? Probably is it worth changing
the spec so that the behavior aligns with other DOM features?

+    [ImplementedInPrivateScript] inherit attribute unrestricted double y;
+    [ImplementedInPrivateScript] inherit attribute unrestricted double z;
+    [ImplementedInPrivateScript] inherit attribute unrestricted double w;
+};
+
+