Ensure that privates are private.

extensions/renderer/resources/messaging.js

Index: extensions/renderer/resources/messaging.js
diff --git a/extensions/renderer/resources/messaging.js b/extensions/renderer/resources/messaging.js
index 3b98432f887000fbfeba505e28bf17c28645c300..e943b4d5abc25ae6b74aa324e83dd4e3631ea33e 100644
--- a/extensions/renderer/resources/messaging.js
+++ b/extensions/renderer/resources/messaging.js
@@ -400,15 +400,21 @@
     return alignedArgs;
   }
 
-var Port = utils.expose('Port', PortImpl, { functions: [
-    'disconnect',
-    'postMessage'
-  ],
-  properties: [
-    'name',
-    'onDisconnect',
-    'onMessage'
-  ] });
+  function Port() {
+    privates(Port).constructPrivate(this, arguments);
+  }
+  utils.expose(Port, PortImpl, {
+    __proto__: null,
+    functions: [
+      'disconnect',
+      'postMessage',
+    ],
+    properties: [
+      'name',
+      'onDisconnect',
+      'onMessage',
+    ],
+  });
 
 exports.$set('kRequestChannel', kRequestChannel);
 exports.$set('kMessageChannel', kMessageChannel);