Refactor Windows MessageBox fallback code.

chrome/browser/ui/views/simple_message_box_win.cc

-// 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.
-
-#include "chrome/browser/ui/simple_message_box.h"
-
-#include "ui/base/win/message_box_win.h"
-
-namespace chrome {
-
-MessageBoxResult NativeShowMessageBox(HWND parent,
-                                      const base::string16& title,
-                                      const base::string16& message,
-                                      MessageBoxType type) {
-  UINT flags = MB_SETFOREGROUND;
-  if (type == MESSAGE_BOX_TYPE_QUESTION) {
-    flags |= MB_YESNO;
-  } else if (type == MESSAGE_BOX_TYPE_OK_CANCEL) {
-    flags |= MB_OKCANCEL;
-  } else {
-    flags |= MB_OK;
-  }
-  flags |= ((type == MESSAGE_BOX_TYPE_INFORMATION) ?
-      MB_ICONINFORMATION : MB_ICONWARNING);
-  int result = ui::MessageBox(parent, message, title, flags);
-  return (result == IDYES || result == IDOK) ?
-      MESSAGE_BOX_RESULT_YES : MESSAGE_BOX_RESULT_NO;
-}
-
-}  // namespace chrome