Pages still shown in pageIds key after being closed

Just a note here: closing a page in your browser (or through a script) essentially closes the websocket for that page. On the backend, this registers as a connection loss, and we give the page 60 seconds (by default) to reconnect. During that 60 seconds, the page will still show as part of the session. After the 60 seconds have elapsed, we remove the page from the listings.