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

base/basictypes.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_BASICTYPES_H_
 #define BASE_BASICTYPES_H_
-#pragma once
 
 #include <limits.h>         // So we can set the bounds of our types
 #include <stddef.h>         // For size_t
 #include <string.h>         // for memcpy
 
 #include "base/port.h"    // Types that only need exist on certain systems
 
 #ifndef COMPILER_MSVC
 // stdint.h is part of C99 but MSVC doesn't have it.
 #include <stdint.h>         // For intptr_t.
@@ skipping 335 matching lines @@
 
 // Use these to declare and define a static local variable (static T;) so that
 // it is leaked so that its destructors are not called at exit. If you need
 // thread-safe initialization, use base/lazy_instance.h instead.
 #define CR_DEFINE_STATIC_LOCAL(type, name, arguments) \
   static type& name = *new type arguments
 
 }  // base
 
 #endif  // BASE_BASICTYPES_H_