Revert of Stop passing const-reference of SWRegistration in all GetRegistrationsCallbacks.

content/browser/background_sync/background_sync_manager.cc

 // Copyright 2015 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.
 
 #include "content/browser/background_sync/background_sync_manager.h"
 
 #include <utility>
 
 #include "base/barrier_closure.h"
 #include "base/bind.h"
@@ skipping 956 matching lines @@
                    events_completed_barrier_closure));
   }
 }
 
 void BackgroundSyncManager::FireReadyEventsDidFindRegistration(
     const std::string& tag,
     BackgroundSyncRegistration::RegistrationId registration_id,
     const base::Closure& event_fired_callback,
     const base::Closure& event_completed_callback,
     ServiceWorkerStatusCode service_worker_status,
-    scoped_refptr<ServiceWorkerRegistration> service_worker_registration) {
+    const scoped_refptr<ServiceWorkerRegistration>&
+        service_worker_registration) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   if (service_worker_status != SERVICE_WORKER_OK) {
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE, base::Bind(event_fired_callback));
     base::ThreadTaskRunnerHandle::Get()->PostTask(
         FROM_HERE, base::Bind(event_completed_callback));
     return;
   }
 
   BackgroundSyncRegistration* registration =
@@ skipping 199 matching lines @@
   parameters_->max_sync_attempts = max_attempts;
   base::ThreadTaskRunnerHandle::Get()->PostTask(FROM_HERE, callback);
 }
 
 base::Closure BackgroundSyncManager::MakeEmptyCompletion() {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   return op_scheduler_.WrapCallbackToRunNext(base::Bind(&base::DoNothing));
 }
 
 }  // namespace content