Remove #pragma once from sync

sync/internal_api/public/base/enum_set.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_INTERNAL_API_PUBLIC_BASE_ENUM_SET_H_
 #define SYNC_INTERNAL_API_PUBLIC_BASE_ENUM_SET_H_
-#pragma once
 
 #include <bitset>
 #include <cstddef>
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/logging.h"
 
 namespace syncer {
 
@@ skipping 259 matching lines @@
 
 template <typename E, E Min, E Max>
 EnumSet<E, Min, Max> Difference(EnumSet<E, Min, Max> set1,
                                 EnumSet<E, Min, Max> set2) {
   return EnumSet<E, Min, Max>(set1.enums_ & ~set2.enums_);
 }
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_BASE_ENUM_SET_H_