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

base/atomicops_internals_atomicword_compat.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.
 
 // This file is an internal atomic implementation, use base/atomicops.h instead.
 
 #ifndef BASE_ATOMICOPS_INTERNALS_ATOMICWORD_COMPAT_H_
 #define BASE_ATOMICOPS_INTERNALS_ATOMICWORD_COMPAT_H_
-#pragma once
 
 // AtomicWord is a synonym for intptr_t, and Atomic32 is a synonym for int32,
 // which in turn means int. On some LP32 platforms, intptr_t is an int, but
 // on others, it's a long. When AtomicWord and Atomic32 are based on different
 // fundamental types, their pointers are incompatible.
 //
 // This file defines function overloads to allow both AtomicWord and Atomic32
 // data to be used with this interface.
 //
 // On LP64 platforms, AtomicWord and Atomic64 are both always long,
@@ skipping 72 matching lines @@
   return base::subtle::Release_Load(
       reinterpret_cast<volatile const Atomic32*>(ptr));
 }
 
 }   // namespace base::subtle
 }   // namespace base
 
 #endif  // !defined(ARCH_CPU_64_BITS)
 
 #endif  // BASE_ATOMICOPS_INTERNALS_ATOMICWORD_COMPAT_H_