js alerts on webview are silently ignored

This breaks pages/sites that use alerts, such as confirmations before a delete and similar.

According to [this answer](https://stackoverflow.com/questions/38931626/javascript-alert-and-confirm-popups-not-working-with-webkit-in-ios-9#38931713) the webview should use a delegate to make it work. I am not versed in iOS, so I am not sure if that is the proper solution.

Start by locating where the iOS webview is created and how its delegate is configured. Reproduce a page using JavaScript alert and confirm dialogs, then verify that those dialogs are no longer silently ignored and that confirmation flows work as expected.

Written by the indexing model from the issue text.