[Sync] Move thread checking into the ModelSafeWorker interface.

chrome/browser/sync/profile_sync_test_util.cc

 // Copyright (c) 2011 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_test_util.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ skipping 37 matching lines @@
   init_params.oauth2_token_service =
       ProfileOAuth2TokenServiceFactory::GetForProfile(profile);
   init_params.start_behavior = ProfileSyncService::MANUAL_START;
   init_params.sync_client = std::move(sync_client);
   init_params.network_time_update_callback =
       base::Bind(&browser_sync::EmptyNetworkTimeUpdate);
   init_params.base_directory = profile->GetPath();
   init_params.url_request_context = profile->GetRequestContext();
   init_params.debug_identifier = profile->GetDebugName();
   init_params.channel = chrome::GetChannel();
-  init_params.db_thread = content::BrowserThread::GetTaskRunnerForThread(
-      content::BrowserThread::DB);
-  init_params.file_thread = content::BrowserThread::GetTaskRunnerForThread(
-      content::BrowserThread::FILE);
   init_params.blocking_pool = content::BrowserThread::GetBlockingPool();
 
   return init_params;
 }
 
 std::unique_ptr<TestingProfile> MakeSignedInTestingProfile() {
   auto profile = base::MakeUnique<TestingProfile>();
   SigninManagerFactory::GetForProfile(profile.get())
       ->SetAuthenticatedAccountInfo("12345", "foo");
   return profile;
 }
 
 std::unique_ptr<KeyedService> BuildMockProfileSyncService(
     content::BrowserContext* context) {
   return base::MakeUnique<browser_sync::ProfileSyncServiceMock>(
       CreateProfileSyncServiceParamsForTest(
           Profile::FromBrowserContext(context)));
 }