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

base/atomicops_internals_x86_msvc.h

 // Copyright (c) 2006-2008 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.
 
 // This file is an internal atomic implementation, use base/atomicops.h instead.
 
 #ifndef BASE_ATOMICOPS_INTERNALS_X86_MSVC_H_
 #define BASE_ATOMICOPS_INTERNALS_X86_MSVC_H_
-#pragma once
 
 #include <windows.h>
 
 namespace base {
 namespace subtle {
 
 inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
                                          Atomic32 old_value,
                                          Atomic32 new_value) {
   LONG result = InterlockedCompareExchange(
@@ skipping 152 matching lines @@
   return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
 }
 
 
 #endif  // defined(_WIN64)
 
 }  // namespace base::subtle
 }  // namespace base
 
 #endif  // BASE_ATOMICOPS_INTERNALS_X86_MSVC_H_