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

base/win/wrapped_window_proc.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.
 
 // Provides a way to handle exceptions that happen while a WindowProc is
 // running. The behavior of exceptions generated inside a WindowProc is OS
 // dependent, but it is possible that the OS just ignores the exception and
 // continues execution, which leads to unpredictable behavior for Chrome.
 
 #ifndef BASE_WIN_WRAPPED_WINDOW_PROC_H_
 #define BASE_WIN_WRAPPED_WINDOW_PROC_H_
-#pragma once
 
 #include <windows.h>
 
 #include "base/base_export.h"
 #include "base/string16.h"
 
 namespace base {
 namespace win {
 
 // An exception filter for a WindowProc. The return value determines how the
@@ skipping 54 matching lines @@
     rv = proc(hwnd, message, wparam, lparam);
   } __except(CallExceptionFilter(GetExceptionInformation())) {
   }
   return rv;
 }
 
 }  // namespace win
 }  // namespace base
 
 #endif  // BASE_WIN_WRAPPED_WINDOW_PROC_H_