Adding fromPoint to DOMPoint and DOMPointReadOnly interfaces following spec.

third_party/WebKit/Source/core/dom/DOMPointReadOnly.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.
 
 // https://dev.w3.org/fxtf/geometry/#DOMPoint
 
 [
     Constructor(unrestricted double x, unrestricted double y,
                 unrestricted double z, unrestricted double w),
     // FIXME: Exposed=(Window,Worker)
     RuntimeEnabled=GeometryInterfaces,
 ] interface DOMPointReadOnly {
+    [NewObject] static DOMPointReadOnly fromPoint(optional DOMPointInit other);
+
     readonly attribute unrestricted double x;
     readonly attribute unrestricted double y;
     readonly attribute unrestricted double z;
     readonly attribute unrestricted double w;
 
     // FIXME: Implement matrixTransform.
     // DOMPoint matrixTransform(DOMMatrixReadOnly matrix);
 };