Remove #pragma once from sync

sync/syncable/directory_backing_store.h

 // Copyright (c) 2012 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 SYNC_SYNCABLE_DIRECTORY_BACKING_STORE_H_
 #define SYNC_SYNCABLE_DIRECTORY_BACKING_STORE_H_
-#pragma once
 
 #include <string>
 
 #include "base/memory/scoped_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "sql/connection.h"
 #include "sql/statement.h"
 #include "sync/internal_api/public/base/model_type.h"
 #include "sync/syncable/dir_open_result.h"
 #include "sync/syncable/directory.h"
@@ skipping 142 matching lines @@
   // discarded.
   bool needs_column_refresh_;
 
   DISALLOW_COPY_AND_ASSIGN(DirectoryBackingStore);
 };
 
 }  // namespace syncable
 }  // namespace syncer
 
 #endif  // SYNC_SYNCABLE_DIRECTORY_BACKING_STORE_H_