Remove #pragma once from crypto

crypto/secure_util.h

 // Copyright (c) 2011 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 CRYPTO_SECURE_UTIL_H_
 #define CRYPTO_SECURE_UTIL_H_
-#pragma once
 
 #include <stddef.h>
 
 #include "crypto/crypto_export.h"
 
 namespace crypto {
 
 // Performs a constant-time comparison of two strings, returning true if the
 // strings are equal.
 //
 // For cryptographic operations, comparison functions such as memcmp() may
 // expose side-channel information about input, allowing an attacker to
 // perform timing analysis to determine what the expected bits should be. In
 // order to avoid such attacks, the comparison must execute in constant time,
 // so as to not to reveal to the attacker where the difference(s) are.
 // For an example attack, see
 // http://groups.google.com/group/keyczar-discuss/browse_thread/thread/5571eca0948b2a13
 CRYPTO_EXPORT bool SecureMemEqual(const void* s1, const void* s2, size_t n);
 
 }  // namespace crypto
 
 #endif  // CRYPTO_SECURE_UTIL_H_