Remove #pragma once from sync

sync/engine/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_SYNCER_COMMAND_H_
 #define SYNC_ENGINE_SYNCER_COMMAND_H_
-#pragma once
 
 #include "base/basictypes.h"
 
 #include "sync/internal_api/public/util/syncer_error.h"
 
 namespace syncer {
 
 namespace sessions {
 class SyncSession;
 }
@@ skipping 20 matching lines @@
 
   // ExecuteImpl is where derived classes actually do work.
   virtual SyncerError ExecuteImpl(sessions::SyncSession* session) = 0;
  private:
   DISALLOW_COPY_AND_ASSIGN(SyncerCommand);
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_ENGINE_SYNCER_COMMAND_H_