When viewing an app in a web browser, the app will timeout after a certain duration. Then a small dialog will pop up telling you to restart the app. Previously, the app would continue to remain open, but be disconnected from datasources and you wouldn't know it. So the implementation of the dialog box is good.
I suggest a way for web browser users to renew their session without restarting the app. Suppose you are near the end of the available time to use the app, but you need to complete something on it before it restarts. You would be booted off and lose your progress. It would be useful to renew the session so that you don't lose your progress.