Remove #pragma once from sync

sync/api/sync_change_processor.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_API_SYNC_CHANGE_PROCESSOR_H_
 #define SYNC_API_SYNC_CHANGE_PROCESSOR_H_
-#pragma once
 
 #include <vector>
 
 #include "sync/api/sync_error.h"
 
 namespace tracked_objects {
 class Location;
 }  // namespace tracked_objects
 
 namespace syncer {
@@ skipping 16 matching lines @@
   //   |from_here|: allows tracking of where sync changes originate.
   //   |change_list|: is the list of sync changes in need of processing.
   virtual SyncError ProcessSyncChanges(
       const tracked_objects::Location& from_here,
       const SyncChangeList& change_list) = 0;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_API_SYNC_CHANGE_PROCESSOR_H_