Implement DOMPoint using v8 extras.

third_party/WebKit/Source/modules/geometry/DOMPointReadOnly.js

+// Copyright 2016 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.
+
+(function(global, binding, v8) {
+  'use strict';
+
+  const defineProperty = global.Object.defineProperty;
+
+  class DOMPointReadOnly {
+    constructor(x = 0, y = 0, z = 0, w = 1) {
+      defineProperty(this, 'x', {
+        value: x,
+        configurable: true,
+        enumerable: true,
+        writable: false
+      });
+
+      defineProperty(this, 'y', {
+        value: y,
+        configurable: true,
+        enumerable: true,
+        writable: false
+      });
+
+      defineProperty(this, 'z', {
+        value: z,
+        configurable: true,
+        enumerable: true,
+        writable: false
+      });
+
+      defineProperty(this, 'w', {
+        value: w,
+        configurable: true,
+        enumerable: true,
+        writable: false
+      });
+    }
+
+    static fromPoint(init) {
+      return new DOMPointReadOnly(init.x, init.y, init.z, init.w);
+    }
+  }
+
+  binding.createDOMPointReadOnly = DOMPointReadOnly.fromPoint;
+
+  defineProperty(global, 'DOMPointReadOnly', {
+    value: DOMPointReadOnly,
+    configurable: true,
+    enumerable: false,
+    writable: true
+  });
+});