[BackgroundSync]: Resolve the register promise before firing sync events

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 669 matching lines @@
   }
 
   BackgroundSyncMetrics::RegistrationCouldFire registration_could_fire =
       AreOptionConditionsMet(*new_registration.options())
           ? BackgroundSyncMetrics::REGISTRATION_COULD_FIRE
           : BackgroundSyncMetrics::REGISTRATION_COULD_NOT_FIRE;
   BackgroundSyncMetrics::CountRegisterSuccess(
       registration_could_fire,
       BackgroundSyncMetrics::REGISTRATION_IS_NOT_DUPLICATE);
 
-  FireReadyEvents();
-
-  base::ThreadTaskRunnerHandle::Get()->PostTask(
+  base::ThreadTaskRunnerHandle::Get()->PostTaskAndReply(
       FROM_HERE,
       base::Bind(callback, BACKGROUND_SYNC_STATUS_OK,
                  base::Passed(base::MakeUnique<BackgroundSyncRegistration>(
-                     new_registration))));
+                     new_registration))),
+      base::Bind(&BackgroundSyncManager::FireReadyEvents,
+                 weak_ptr_factory_.GetWeakPtr()));
 }
 
 void BackgroundSyncManager::RemoveActiveRegistration(int64_t sw_registration_id,
                                                      const std::string& tag) {
   DCHECK_CURRENTLY_ON(BrowserThread::IO);
   DCHECK(LookupActiveRegistration(sw_registration_id, tag));
 
   BackgroundSyncRegistrations* registrations =
       &active_registrations_[sw_registration_id];
 
@@ skipping 464 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