I've recently noticed that if a PWA, bookmarked to the home screen of my Android phone triggers any JavaScript dialogue boxes, it introduces a random browser element at the top of the screen:
Screenshot showing unexpected browser controls/title bar
The title and URL of the page is shown, but the close, settings and more icons are not functional/don't react to touch events.
I have the webmanifest display set to 'standalone', and this behaviour didn't happen until a recent update to Chrome, it seems.
I have reviewed the webmanifest documentation, but can't see any settings that could address this behaviour, which wasn't present until recently.
EDIT: This seems to have been an oddity in Chrome, and it is no longer appearing :)