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

base/linux_util.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 BASE_LINUX_UTIL_H_
 #define BASE_LINUX_UTIL_H_
-#pragma once
 
 #include <stdint.h>
 #include <sys/types.h>
 
 #include <string>
 
 #include "base/base_export.h"
 
 namespace base {
 
@@ skipping 26 matching lines @@
 // |expected_data|, where N is the length of |expected_data|.
 // Returns the thread id or -1 on error.  If |syscall_supported| is
 // set to false the kernel does not support syscall in procfs.
 BASE_EXPORT pid_t FindThreadIDWithSyscall(pid_t pid,
                                           const std::string& expected_data,
                                           bool* syscall_supported);
 
 }  // namespace base
 
 #endif  // BASE_LINUX_UTIL_H_