clang/win: Let some chromium_code targets build with -Wextra.

base/win/startup_information.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_WIN_STARTUP_INFORMATION_H_
 #define BASE_WIN_STARTUP_INFORMATION_H_
 
 #include <windows.h>
 
 #include "base/base_export.h"
@@ skipping 13 matching lines @@
   bool InitializeProcThreadAttributeList(DWORD attribute_count);
 
   // Sets one entry in the initialized attribute list.
   // |value| needs to live at least as long as the StartupInformation object
   // this is called on.
   bool UpdateProcThreadAttribute(DWORD_PTR attribute,
                                  void* value,
                                  size_t size);
 
   LPSTARTUPINFOW startup_info() { return &startup_info_.StartupInfo; }
-  const LPSTARTUPINFOW startup_info() const {
+  LPSTARTUPINFOW startup_info() const {
     return const_cast<const LPSTARTUPINFOW>(&startup_info_.StartupInfo);
   }
 
   bool has_extended_startup_info() const {
     return !!startup_info_.lpAttributeList;
   }
 
  private:
   STARTUPINFOEXW startup_info_;
   DISALLOW_COPY_AND_ASSIGN(StartupInformation);
 };
 
 }  // namespace win
 }  // namespace base
 
 #endif  // BASE_WIN_STARTUP_INFORMATION_H_