Remove #pragma once from sync

sync/engine/model_changing_syncer_command.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_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_
 #define SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_
-#pragma once
 
 #include "base/compiler_specific.h"
 #include "sync/engine/syncer_command.h"
 #include "sync/internal_api/public/engine/model_safe_worker.h"
 
 namespace syncer {
 namespace sessions {
 class SyncSession;
 }
 
@@ skipping 50 matching lines @@
   // Implementations will implement ModelChangingExecuteImpl and not
   // worry about storing the session or setting it. They are given work_session.
   sessions::SyncSession* work_session_;
 
   DISALLOW_COPY_AND_ASSIGN(ModelChangingSyncerCommand);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_MODEL_CHANGING_SYNCER_COMMAND_H_