Implement a poor man's PostAfterStartupTask() function.

content/browser/service_worker/service_worker_register_job.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_REGISTER_JOB_H_
 #define CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_REGISTER_JOB_H_
 
 #include <vector>
 
 #include "base/memory/weak_ptr.h"
@@ skipping 86 matching lines @@
     scoped_refptr<ServiceWorkerVersion> new_version;
   };
 
   void set_registration(
       const scoped_refptr<ServiceWorkerRegistration>& registration);
   ServiceWorkerRegistration* registration();
   void set_new_version(ServiceWorkerVersion* version);
   ServiceWorkerVersion* new_version();
 
   void SetPhase(Phase phase);
+  void StartInternal();
 
   void ContinueWithRegistration(
       ServiceWorkerStatusCode status,
       const scoped_refptr<ServiceWorkerRegistration>& registration);
   void ContinueWithUpdate(
       ServiceWorkerStatusCode status,
       const scoped_refptr<ServiceWorkerRegistration>& registration);
   void RegisterAndContinue();
   void ContinueWithUninstallingRegistration(
       const scoped_refptr<ServiceWorkerRegistration>& existing_registration,
@@ skipping 44 matching lines @@
   std::string promise_resolved_status_message_;
   scoped_refptr<ServiceWorkerRegistration> promise_resolved_registration_;
   base::WeakPtrFactory<ServiceWorkerRegisterJob> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ServiceWorkerRegisterJob);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_SERVICE_WORKER_SERVICE_WORKER_REGISTER_JOB_H_