Set up the infrastructure for Extension event metrics.

extensions/browser/api/bluetooth/bluetooth_api_pairing_delegate.cc

Index: extensions/browser/api/bluetooth/bluetooth_api_pairing_delegate.cc
diff --git a/extensions/browser/api/bluetooth/bluetooth_api_pairing_delegate.cc b/extensions/browser/api/bluetooth/bluetooth_api_pairing_delegate.cc
index 7ffbe632b793261e20f28b2d4a736694be47329f..d08f7193d10331937db4f206bd3dd2c500c4b28c 100644
--- a/extensions/browser/api/bluetooth/bluetooth_api_pairing_delegate.cc
+++ b/extensions/browser/api/bluetooth/bluetooth_api_pairing_delegate.cc
@@ -102,8 +102,8 @@ void BluetoothApiPairingDelegate::DispatchPairingEvent(
     const bt_private::PairingEvent& pairing_event) {
   scoped_ptr<base::ListValue> args =
       bt_private::OnPairing::Create(pairing_event);
-  scoped_ptr<Event> event(
-      new Event(bt_private::OnPairing::kEventName, args.Pass()));
+  scoped_ptr<Event> event(new Event(
+      events::UNKNOWN, bt_private::OnPairing::kEventName, args.Pass()));
   EventRouter::Get(browser_context_)
       ->DispatchEventToExtension(extension_id_, event.Pass());
 }