title: User no longer anonymous after app restart in Flutter
body: <p>I start the app and sign the user anonymously with <code>FirebaseAuth.instance.signInAnonymously()</code>.
  The user gets an id, for example &quot;<code>ABC</code>&quot; and <code>isAnonymous</code> is true (obviously).</p>
  <p>The problem is, when I restart (ctrl+shift+F5) an app, the user is still here (because data is persisted), he still has his previous id, except, <code>isAnonymous</code> is no longer true.</p>
  <p>Why is he no longer anonymous after the app restart?</p>
  <p>To summarize:</p>
  <p>Sign in user anonymously <strong>-&gt;</strong> user gets an id and is anonymous <strong>-&gt;</strong> restart an app <strong>-&gt;</strong> the user is still here with his id but is no longer anonymous</p>