[Sync] ModelTypeStore factory shouldn't require valid PSS to function correctly

chrome/browser/sync/profile_sync_service_factory.cc

 // Copyright (c) 2012 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 "chrome/browser/sync/profile_sync_service_factory.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/memory/singleton.h"
@@ skipping 131 matching lines @@
     content::BrowserContext* context) const {
   ProfileSyncService::InitParams init_params;
 
   Profile* profile = Profile::FromBrowserContext(context);
 
   init_params.network_time_update_callback = base::Bind(&UpdateNetworkTime);
   init_params.base_directory = profile->GetPath();
   init_params.url_request_context = profile->GetRequestContext();
   init_params.debug_identifier = profile->GetDebugName();
   init_params.channel = chrome::GetChannel();
-  base::SequencedWorkerPool* blocking_pool =
-      content::BrowserThread::GetBlockingPool();
-  init_params.blocking_task_runner =
-      blocking_pool->GetSequencedTaskRunnerWithShutdownBehavior(
-          blocking_pool->GetSequenceToken(),
-          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
 
   if (!client_factory_) {
     init_params.sync_client =
         base::MakeUnique<browser_sync::ChromeSyncClient>(profile);
   } else {
     init_params.sync_client = client_factory_->Run(profile);
   }
 
   bool local_sync_backend_enabled = false;
 // Since the local sync backend is currently only supported on Windows don't
@@ skipping 62 matching lines @@
 
 // static
 void ProfileSyncServiceFactory::SetSyncClientFactoryForTest(
     SyncClientFactory* client_factory) {
   client_factory_ = client_factory;
 }
 
 // static
 ProfileSyncServiceFactory::SyncClientFactory*
     ProfileSyncServiceFactory::client_factory_ = nullptr;