Remove #pragma once. Just from base/ for now.

base/safe_strerror_posix.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 BASE_SAFE_STRERROR_POSIX_H_
 #define BASE_SAFE_STRERROR_POSIX_H_
-#pragma once
 
 #include <string>
 
 #include "base/base_export.h"
 
 // BEFORE using anything from this file, first look at PLOG and friends in
 // logging.h and use them instead if applicable.
 //
 // This file declares safe, portable alternatives to the POSIX strerror()
 // function. strerror() is inherently unsafe in multi-threaded apps and should
@@ skipping 12 matching lines @@
 
 // Calls safe_strerror_r with a buffer of suitable size and returns the result
 // in a C++ string.
 //
 // Use this instead of strerror(). Note though that safe_strerror_r will be
 // more robust in the case of heap corruption errors, since it doesn't need to
 // allocate a string.
 BASE_EXPORT std::string safe_strerror(int err);
 
 #endif  // BASE_SAFE_STRERROR_POSIX_H_