[Sync] Pass a TaskRunner into SBHI/SBHC, not a thread or message loop.

components/sync/driver/glue/sync_backend_host_core.h

 // 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.
 
 #ifndef COMPONENTS_SYNC_DRIVER_GLUE_SYNC_BACKEND_HOST_CORE_H_
 #define COMPONENTS_SYNC_DRIVER_GLUE_SYNC_BACKEND_HOST_CORE_H_
 
 #include <stdint.h>
 
 #include <map>
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "base/single_thread_task_runner.h"
 #include "base/timer/timer.h"
 #include "base/trace_event/memory_dump_provider.h"
 #include "components/invalidation/public/invalidation.h"
 #include "components/sync/base/cancelation_signal.h"
 #include "components/sync/base/system_encryptor.h"
 #include "components/sync/driver/glue/sync_backend_host_impl.h"
 #include "components/sync/engine/cycle/type_debug_info_observer.h"
 #include "components/sync/engine/shutdown_reason.h"
 #include "components/sync/engine/sync_encryption_handler.h"
 #include "url/gurl.h"
 
 namespace syncer {
 
 class SyncBackendHostImpl;
 
 // Utility struct for holding initialization options.
 struct DoInitializeOptions {
   DoInitializeOptions(
-      base::MessageLoop* sync_loop,
+      scoped_refptr<base::SingleThreadTaskRunner> sync_task_runner,
       SyncBackendRegistrar* registrar,
       const std::vector<scoped_refptr<ModelSafeWorker>>& workers,
       const scoped_refptr<ExtensionsActivity>& extensions_activity,
       const WeakHandle<JsEventHandler>& event_handler,
       const GURL& service_url,
       const std::string& sync_user_agent,
       std::unique_ptr<HttpPostProviderFactory> http_bridge_factory,
       const SyncCredentials& credentials,
       const std::string& invalidator_client_id,
       std::unique_ptr<SyncManagerFactory> sync_manager_factory,
       bool delete_sync_data_folder,
       bool enable_local_sync_backend,
       const base::FilePath& local_sync_backend_folder,
       const std::string& restored_key_for_bootstrapping,
       const std::string& restored_keystore_key_for_bootstrapping,
       std::unique_ptr<EngineComponentsFactory> engine_components_factory,
       const WeakHandle<UnrecoverableErrorHandler>& unrecoverable_error_handler,
       const base::Closure& report_unrecoverable_error_function,
       std::unique_ptr<SyncEncryptionHandler::NigoriState> saved_nigori_state,
       const std::map<ModelType, int64_t>& invalidation_versions);
   ~DoInitializeOptions();
 
-  base::MessageLoop* sync_loop;
+  scoped_refptr<base::SingleThreadTaskRunner> sync_task_runner;
   SyncBackendRegistrar* registrar;
   std::vector<scoped_refptr<ModelSafeWorker>> workers;
   scoped_refptr<ExtensionsActivity> extensions_activity;
   WeakHandle<JsEventHandler> event_handler;
   GURL service_url;
   std::string sync_user_agent;
   // Overridden by tests.
   std::unique_ptr<HttpPostProviderFactory> http_bridge_factory;
   SyncCredentials credentials;
   const std::string invalidator_client_id;
@@ skipping 201 matching lines @@
 
   // Name used for debugging.
   const std::string name_;
 
   // Path of the folder that stores the sync data files.
   const base::FilePath sync_data_folder_path_;
 
   // Our parent SyncBackendHost.
   WeakHandle<SyncBackendHostImpl> host_;
 
-  // The loop where all the sync backend operations happen.
-  // Non-null only between calls to DoInitialize() and ~Core().
-  base::MessageLoop* sync_loop_;
+  // The task runner where all the sync engine operations happen.
+  scoped_refptr<base::SingleThreadTaskRunner> sync_task_runner_;
 
   // Our parent's registrar (not owned).  Non-null only between
   // calls to DoInitialize() and DoShutdown().
   SyncBackendRegistrar* registrar_;
 
   // The timer used to periodically call SaveChanges.
   std::unique_ptr<base::RepeatingTimer> save_changes_timer_;
 
   // Our encryptor, which uses Chrome's encryption functions.
   SystemEncryptor encryptor_;
@@ skipping 32 matching lines @@
   std::map<ModelType, int64_t> last_invalidation_versions_;
 
   base::WeakPtrFactory<SyncBackendHostCore> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncBackendHostCore);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DRIVER_GLUE_SYNC_BACKEND_HOST_CORE_H_