Fix build error with gcc 4.8.2 about WARN_UNUSED_RESULT

chrome/browser/dom_distiller/dom_distiller_service_factory.cc

 // 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.
 
 #include "chrome/browser/dom_distiller/dom_distiller_service_factory.h"
 
 #include <utility>
 
 #include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/profiles/incognito_helpers.h"
@@ skipping 37 matching lines @@
     : BrowserContextKeyedServiceFactory(
           "DomDistillerService",
           BrowserContextDependencyManager::GetInstance()) {}
 
 DomDistillerServiceFactory::~DomDistillerServiceFactory() {}
 
 KeyedService* DomDistillerServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* profile) const {
   scoped_refptr<base::SequencedTaskRunner> background_task_runner =
       content::BrowserThread::GetBlockingPool()->GetSequencedTaskRunner(
-          content::BrowserThread::GetBlockingPool()->GetSequenceToken());
+          base::SequencedWorkerPool::GetSequenceToken());
 
   scoped_ptr<leveldb_proto::ProtoDatabaseImpl<ArticleEntry> > db(
       new leveldb_proto::ProtoDatabaseImpl<ArticleEntry>(
           background_task_runner));
 
   base::FilePath database_dir(
       profile->GetPath().Append(FILE_PATH_LITERAL("Articles")));
 
   scoped_ptr<DomDistillerStore> dom_distiller_store(
       new DomDistillerStore(std::move(db), database_dir));
@@ skipping 26 matching lines @@
   return service;
 }
 
 content::BrowserContext* DomDistillerServiceFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
   // Makes normal profile and off-the-record profile use same service instance.
   return chrome::GetBrowserContextRedirectedInIncognito(context);
 }
 
 }  // namespace dom_distiller