title: How to pass information from AppEngine to a Chrome Extension
body: <p>I have a Chrome extension that uses AppEngine as the backend, and uses Google Account for authentication. The extension pops up notifications every 15 minutes, and stores the results in AppEngine. Whenever the notification pops up, I would like to check to make sure that the user is logged in. If they aren't logged in, then I open a page in AppEngine for them to log in.</p>
  
  <p>I would then like to have a way for AppEngine to call back to the extension to tell it to pop up the notification again. Is there any way to do that?</p>