[Sync] Move thread checking into the ModelSafeWorker interface.

components/sync/driver/glue/sync_backend_host_mock.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 "components/sync/driver/glue/sync_backend_host_mock.h"
 
 #include "components/sync/driver/sync_frontend.h"
 #include "components/sync/engine/activation_context.h"
 
 namespace syncer {
 
 const char kTestCacheGuid[] = "test-guid";
 
 SyncBackendHostMock::SyncBackendHostMock() : fail_initial_download_(false) {}
 SyncBackendHostMock::~SyncBackendHostMock() {}
 
 void SyncBackendHostMock::Initialize(
     SyncFrontend* frontend,
     base::Thread* sync_thread,
-    const scoped_refptr<base::SingleThreadTaskRunner>& db_thread,
-    const scoped_refptr<base::SingleThreadTaskRunner>& file_thread,
     const WeakHandle<JsEventHandler>& event_handler,
     const GURL& service_url,
     const std::string& sync_user_agent,
     const SyncCredentials& credentials,
     bool delete_sync_data_folder,
     bool enable_local_sync_backend,
     const base::FilePath& local_sync_backend_folder,
     std::unique_ptr<SyncManagerFactory> sync_manager_factory,
     const WeakHandle<UnrecoverableErrorHandler>& unrecoverable_error_handler,
     const base::Closure& report_unrecoverable_error_function,
@@ skipping 101 matching lines @@
 
 void SyncBackendHostMock::ClearServerData(
     const SyncManager::ClearServerDataCallback& callback) {
   callback.Run();
 }
 
 void SyncBackendHostMock::OnCookieJarChanged(bool account_mismatch,
                                              bool empty_jar) {}
 
 }  // namespace syncer