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..0ba408d9e82dae617c369e73ecc1d03c91487c35 100644
--- a/chrome/renderer/resources/extensions/automation/automation_event.js
+++ b/chrome/renderer/resources/extensions/automation/automation_event.js
@@ -19,8 +19,18 @@ 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, {
+  functions: [
+    'stopPropagation',
+  ],
+  readonly: [
+    'type',
+    'target',
+    'eventPhase',
+  ],
+});
+
+exports.$set('AutomationEvent', AutomationEvent);