Add a helper method to create SW SimpleEventCallbacks.

content/browser/push_messaging/push_messaging_router.cc

Index: content/browser/push_messaging/push_messaging_router.cc
diff --git a/content/browser/push_messaging/push_messaging_router.cc b/content/browser/push_messaging/push_messaging_router.cc
index c512cff29cfa166a893ed69f4f39cb91bcf3a320..995b15d9a65fa35ffb393f53aa18ab52d0e754e9 100644
--- a/content/browser/push_messaging/push_messaging_router.cc
+++ b/content/browser/push_messaging/push_messaging_router.cc
@@ -125,8 +125,7 @@ void PushMessagingRouter::DeliverMessageToWorker(
       ServiceWorkerVersion::KILL_ON_TIMEOUT);
 
   service_worker->event_dispatcher()->DispatchPushEvent(
-      payload, base::Bind(&ServiceWorkerVersion::OnSimpleEventFinished,
-                          service_worker, request_id));
+      payload, service_worker->CreateSimpleEventCallback(request_id));
 }
 
 // static