title: Use Google OpenID from Android device without requiring username/password
body: <p>Currently, I can authenticate against my webapp using OpenID (with Google as the provider).  My Android app goes through the usual OpenID authentication flow.  However, I would like to use the Google account associated with the Android device instead of requiring users to type in their username/password.  Is this possible?</p>
  
  <p>I've been playing around with the AccountManager, but it only seems to allow authenticating for Google services.  It may be that I haven't found the appropriate auth token type.</p>