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

base/base_paths.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_BASE_PATHS_H_
 #define BASE_BASE_PATHS_H_
-#pragma once
 
 // This file declares path keys for the base module.  These can be used with
 // the PathService to access various special directories and files.
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include "base/base_paths_win.h"
 #elif defined(OS_MACOSX)
 #include "base/base_paths_mac.h"
@@ skipping 24 matching lines @@
                 // This is $XDG_CACHE_HOME on Linux and
                 // ~/Library/Caches on Mac.
 #endif
 
   PATH_END
 };
 
 }  // namespace base
 
 #endif  // BASE_BASE_PATHS_H_