Ensure that privates are private.

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

Index: chrome/renderer/resources/extensions/automation/automation_event.js
diff --git a/chrome/renderer/resources/extensions/automation/automation_event.js b/chrome/renderer/resources/extensions/automation/automation_event.js
index 7d04ecc438628d07da08dba54affb6cd43d0fb8d..206b0bfab90297a330deb703f31a4eafe5854d0a 100644
--- a/chrome/renderer/resources/extensions/automation/automation_event.js
+++ b/chrome/renderer/resources/extensions/automation/automation_event.js
@@ -19,8 +19,19 @@ AutomationEventImpl.prototype = {
   }
 };
 
-exports.AutomationEvent = utils.expose(
-    'AutomationEvent',
-    AutomationEventImpl,
-    { functions: ['stopPropagation'],
-      readonly: ['type', 'target', 'eventPhase'] });
+function AutomationEvent() {
+  privates(AutomationEvent).constructPrivate(this, arguments);
+}
+utils.expose(AutomationEvent, AutomationEventImpl, {
+  __proto__: null,

[Devlin, 2016/04/22 17:08:21]

We should always do this, right?  Can we move it into expose()?

[robwu, 2016/04/22 17:37:40]

Done. using $Object.setPrototypeOf, NOT by setting __proto__ because this can be
intercepted.

[Devlin, 2016/04/22 18:52:46]

FYI, I hear from V8 experts that Object.defineProperty would also work for
bypassing getters/setters (not saying we should use it here -
Object.setPrototypeOf makes more sense - just a possibly-useful tidbit).

+  functions: [
+    'stopPropagation',
+  ],
+  readonly: [
+    'type',
+    'target',
+    'eventPhase',
+  ],
+});
+
+exports.$set('AutomationEvent', AutomationEvent);