Adding fromPoint to DOMPoint and DOMPointReadOnly interfaces following spec.

third_party/WebKit/Source/core/dom/DOMPointReadOnly.cpp

 // 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.
 
 #include "core/dom/DOMPointReadOnly.h"
 
+#include "core/dom/DOMPointInit.h"
+
 namespace blink {
 
 DOMPointReadOnly* DOMPointReadOnly::create(double x,
                                            double y,
                                            double z,
                                            double w) {
   return new DOMPointReadOnly(x, y, z, w);
 }
 
+DOMPointReadOnly* DOMPointReadOnly::fromPoint(DOMPointInit& other) {
+  return new DOMPointReadOnly(other.x(), other.y(), other.z(), other.w());
+}
+
 DOMPointReadOnly::DOMPointReadOnly(double x, double y, double z, double w)
     : m_x(x), m_y(y), m_z(z), m_w(w) {}
 
 }  // namespace blink