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

base/base_paths_win.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_WIN_H__
 #define BASE_BASE_PATHS_WIN_H__
-#pragma once
 
 // This file declares windows-specific path keys for the base module.
 // These can be used with the PathService to access various special
 // directories and files.
 
 namespace base {
 
 enum {
   PATH_WIN_START = 100,
 
@@ skipping 15 matching lines @@
   DIR_COMMON_APP_DATA,    // W2K, XP, W2K3: "C:\Documents and Settings\
                           // All Users\Application Data".
                           // Vista, W2K8 and above: "C:\ProgramData".
 
   PATH_WIN_END
 };
 
 }  // namespace base
 
 #endif  // BASE_BASE_PATHS_WIN_H__