Ensure default dialog button focus remains after a dialog update.

ui/views/window/dialog_client_view.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 UI_VIEWS_WINDOW_DIALOG_CLIENT_VIEW_H_
 #define UI_VIEWS_WINDOW_DIALOG_CLIENT_VIEW_H_
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "ui/base/ui_base_types.h"
@@ skipping 113 matching lines @@
   // True if we've notified the delegate the window is closing and the delegate
   // allowed the close. In some situations it's possible to get two closes (see
   // http://crbug.com/71940). This is used to avoid notifying the delegate
   // twice, which can have bad consequences.
   bool delegate_allowed_close_ = false;
 
   // Used to prevent unnecessary or potentially harmful changes during
   // SetupLayout(). Everything will be manually updated afterwards.
   bool adding_or_removing_views_ = false;
 
+  // The dialog button with the default focus.
+  View* default_focus_ = nullptr;
+
   DISALLOW_COPY_AND_ASSIGN(DialogClientView);
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_WINDOW_DIALOG_CLIENT_VIEW_H_