Remove #pragma once from sync

sync/util/encryptor.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_UTIL_ENCRYPTOR_H_
 #define SYNC_UTIL_ENCRYPTOR_H_
-#pragma once
 
 #include <string>
 
 namespace syncer {
 
 class Encryptor {
  public:
   // All methods below should be thread-safe.
   virtual bool EncryptString(const std::string& plaintext,
                              std::string* ciphertext) = 0;
 
   virtual bool DecryptString(const std::string& ciphertext,
                              std::string* plaintext) = 0;
 
  protected:
   virtual ~Encryptor() {}
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_UTIL_ENCRYPTOR_H_