Revert of [SyncFS] Post tasks between SyncEngine and SyncWorker

chrome/browser/sync_file_system/drive_backend/sync_engine_context.h

Index: chrome/browser/sync_file_system/drive_backend/sync_engine_context.h
diff --git a/chrome/browser/sync_file_system/drive_backend/sync_engine_context.h b/chrome/browser/sync_file_system/drive_backend/sync_engine_context.h
index fe23f8bac35d0f9d5c83977897b51e23680fee0d..e3e32d67e4722d2460872b58e440a91cb6383cc3 100644
--- a/chrome/browser/sync_file_system/drive_backend/sync_engine_context.h
+++ b/chrome/browser/sync_file_system/drive_backend/sync_engine_context.h
@@ -32,16 +32,14 @@
   SyncEngineContext(
       drive::DriveServiceInterface* drive_service,
       drive::DriveUploaderInterface* drive_uploader,
-      base::SequencedTaskRunner* ui_task_runner,
-      base::SequencedTaskRunner* file_task_runner);
+      base::SequencedTaskRunner* task_runner);
   ~SyncEngineContext();
 
   drive::DriveServiceInterface* GetDriveService();
   drive::DriveUploaderInterface* GetDriveUploader();
   MetadataDatabase* GetMetadataDatabase();
   RemoteChangeProcessor* GetRemoteChangeProcessor();
-  base::SequencedTaskRunner* GetUiTaskRunner();
-  base::SequencedTaskRunner* GetFileTaskRunner();
+  base::SequencedTaskRunner* GetBlockingTaskRunner();
 
   void SetMetadataDatabase(scoped_ptr<MetadataDatabase> metadata_database);
   void SetRemoteChangeProcessor(RemoteChangeProcessor* remote_change_processor);
@@ -54,8 +52,7 @@
   RemoteChangeProcessor* remote_change_processor_;
 
   scoped_ptr<MetadataDatabase> metadata_database_;
-  scoped_refptr<base::SequencedTaskRunner> ui_task_runner_;
-  scoped_refptr<base::SequencedTaskRunner> file_task_runner_;
+  scoped_refptr<base::SequencedTaskRunner> task_runner_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncEngineContext);
 };