Adds an event handler for the LostFocus event. LostFocus runs when
WebView loses focus. In the case where MoveFocusRequested event is
run, the focus is still on WebView when MoveFocusRequested event runs.
LostFocus only runs afterwards when code of the app or default action
of MoveFocusRequested event set focus away from WebView.
Adds an event handler for the LostFocus event. LostFocus runs when WebView loses focus. In the case where MoveFocusRequested event is run, the focus is still on WebView when MoveFocusRequested event runs. LostFocus only runs afterwards when code of the app or default action of MoveFocusRequested event set focus away from WebView.