[Sync] Switch ModelTypeStore* from blocking pool to post_task.h

chrome/browser/chromeos/printing/printers_manager_factory.cc

 // Copyright 2016 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/chromeos/printing/printers_manager_factory.h"
 
 #include <memory>
 #include <utility>
 
 #include "base/debug/dump_without_crashing.h"
@@ skipping 39 matching lines @@
           BrowserContextDependencyManager::GetInstance()) {}
 
 PrintersManagerFactory::~PrintersManagerFactory() {}
 
 PrintersManager* PrintersManagerFactory::BuildServiceInstanceFor(
     content::BrowserContext* browser_context) const {
   Profile* profile = Profile::FromBrowserContext(browser_context);
 
   const syncer::ModelTypeStoreFactory& store_factory =
       browser_sync::ProfileSyncService::GetModelTypeStoreFactory(
-          syncer::PRINTERS, profile->GetPath(),
-          content::BrowserThread::GetBlockingPool());
+          syncer::PRINTERS, profile->GetPath());
 
   std::unique_ptr<PrintersSyncBridge> sync_bridge =
       base::MakeUnique<PrintersSyncBridge>(
           store_factory,
           base::BindRepeating(
               base::IgnoreResult(&base::debug::DumpWithoutCrashing)));
 
   return new PrintersManager(profile, std::move(sync_bridge));
 }
 
 }  // namespace chromeos