Ensure that privates are private.

chrome/renderer/resources/extensions/automation/automation_event.js

 // 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.
 
 var utils = require('utils');
 
 var AutomationEventImpl = function(type, target) {
   this.propagationStopped = false;
 
   // TODO(aboxhall): make these read-only properties
   this.type = type;
   this.target = target;
   this.eventPhase = Event.NONE;
 };
 
 AutomationEventImpl.prototype = {
   stopPropagation: function() {
     this.propagationStopped = true;
   }
 };
 
-exports.AutomationEvent = utils.expose(
-    'AutomationEvent',
-    AutomationEventImpl,
-    { functions: ['stopPropagation'],
-      readonly: ['type', 'target', 'eventPhase'] });
+function AutomationEvent() {
+  privates(AutomationEvent).constructPrivate(this, arguments);
+}
+utils.expose(AutomationEvent, AutomationEventImpl, {
+  functions: [
+    'stopPropagation',
+  ],
+  readonly: [
+    'type',
+    'target',
+    'eventPhase',
+  ],
+});
+
+exports.$set('AutomationEvent', AutomationEvent);