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

base/win/pe_image.h

 // Copyright (c) 2010 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 was adapted from GreenBorder's Code.
 // To understand what this class is about (for other than well known functions
 // as GetProcAddress), a good starting point is "An In-Depth Look into the
 // Win32 Portable Executable File Format" by Matt Pietrek:
 // http://msdn.microsoft.com/msdnmag/issues/02/02/PE/default.aspx
 
 #ifndef BASE_WIN_PE_IMAGE_H_
 #define BASE_WIN_PE_IMAGE_H_
-#pragma once
 
 #include <windows.h>
 
 #if defined(_WIN32_WINNT_WIN8)
 // The Windows 8 SDK defines FACILITY_VISUALCPP in winerror.h.
 #undef FACILITY_VISUALCPP
 #endif
 #include <DelayIMP.h>
 
 namespace base {
@@ skipping 236 matching lines @@
 
 inline PIMAGE_EXPORT_DIRECTORY PEImage::GetExportDirectory() const {
   return reinterpret_cast<PIMAGE_EXPORT_DIRECTORY>(
              GetImageDirectoryEntryAddr(IMAGE_DIRECTORY_ENTRY_EXPORT));
 }
 
 }  // namespace win
 }  // namespace base
 
 #endif  // BASE_WIN_PE_IMAGE_H_