[Sync] Move thread checking into the ModelSafeWorker interface.

components/browser_sync/profile_sync_service_unittest.cc

Index: components/browser_sync/profile_sync_service_unittest.cc
diff --git a/components/browser_sync/profile_sync_service_unittest.cc b/components/browser_sync/profile_sync_service_unittest.cc
index af05fc8c12a874a79e14f75ff00f87b96bdad0dc..d6ac925948a0c07608b80e26c5ab1236e83de588 100644
--- a/components/browser_sync/profile_sync_service_unittest.cc
+++ b/components/browser_sync/profile_sync_service_unittest.cc
@@ -104,8 +104,6 @@ class SyncBackendHostNoReturn : public SyncBackendHostMock {
   void Initialize(
       syncer::SyncFrontend* frontend,
       base::Thread* sync_thread,
-      const scoped_refptr<base::SingleThreadTaskRunner>& db_thread,
-      const scoped_refptr<base::SingleThreadTaskRunner>& file_thread,
       const syncer::WeakHandle<syncer::JsEventHandler>& event_handler,
       const GURL& service_url,
       const std::string& sync_user_agent,
@@ -131,8 +129,6 @@ class SyncBackendHostMockCollectDeleteDirParam : public SyncBackendHostMock {
   void Initialize(
       syncer::SyncFrontend* frontend,
       base::Thread* sync_thread,
-      const scoped_refptr<base::SingleThreadTaskRunner>& db_thread,
-      const scoped_refptr<base::SingleThreadTaskRunner>& file_thread,
       const syncer::WeakHandle<syncer::JsEventHandler>& event_handler,
       const GURL& service_url,
       const std::string& sync_user_agent,
@@ -149,12 +145,11 @@ class SyncBackendHostMockCollectDeleteDirParam : public SyncBackendHostMock {
           saved_nigori_state) override {
     delete_dir_param_->push_back(delete_sync_data_folder);
     SyncBackendHostMock::Initialize(
-        frontend, sync_thread, db_thread, file_thread, event_handler,
-        service_url, sync_user_agent, credentials, delete_sync_data_folder,
-        enable_local_sync_backend, local_sync_backend_folder,
-        std::move(sync_manager_factory), unrecoverable_error_handler,
-        report_unrecoverable_error_function, http_post_provider_factory_getter,
-        std::move(saved_nigori_state));
+        frontend, sync_thread, event_handler, service_url, sync_user_agent,
+        credentials, delete_sync_data_folder, enable_local_sync_backend,
+        local_sync_backend_folder, std::move(sync_manager_factory),
+        unrecoverable_error_handler, report_unrecoverable_error_function,
+        http_post_provider_factory_getter, std::move(saved_nigori_state));
   }
 
  private: