title: Event onBrowserClose for Google Chrome Extension?
body: <p>I am developing an extension for Google Chrome. My background script, everytime, authorizes on a server that uses the XMPP API, and subscribes for a PubSub node. I need to unsubscribe on the exit, otherwise the dummy subscriptions will remain on the server. Is There any <code>onBrowserClose</code> event in the Google Chrome Extension APIs?</p>