Set up the infrastructure for Extension event metrics.

extensions/browser/api/vpn_provider/vpn_service.cc

Index: extensions/browser/api/vpn_provider/vpn_service.cc
diff --git a/extensions/browser/api/vpn_provider/vpn_service.cc b/extensions/browser/api/vpn_provider/vpn_service.cc
index 608d25418c4453d502810a011f4c9927b1183ce1..5eaed3ebd9bff6f308ebb29b1fe9e94e922cedd2 100644
--- a/extensions/browser/api/vpn_provider/vpn_service.cc
+++ b/extensions/browser/api/vpn_provider/vpn_service.cc
@@ -518,7 +518,8 @@ void VpnService::SendSignalToExtension(const std::string& extension_id,
                                        const std::string& event_name,
                                        scoped_ptr<base::ListValue> event_args) {
   scoped_ptr<extensions::Event> event(
-      new extensions::Event(event_name, event_args.Pass(), browser_context_));
+      new extensions::Event(extensions::events::UNKNOWN, event_name,
+                            event_args.Pass(), browser_context_));
 
   event_router_->DispatchEventToExtension(extension_id, event.Pass());
 }