title: userChanges stream in Flutter Fire does not stream profile changes
body: <p>According to <a href="https://pub.dev/documentation/firebase_auth/latest/firebase_auth/FirebaseAuth/userChanges.html" rel="nofollow noreferrer">FlutterFire docs</a>, userChanges should stream any changes to user profile in Firebase. I added the following code to a screen:</p>
  <pre class="lang-dart prettyprint-override"><code>class UserInfo extends StatefulWidget {
    UserInfo({Key key}) : super(key: key);
  
    @override
    _UserInfoState createState() =&gt; _UserInfoState();
  }
  
  class _UserInfoState extends State&lt;UserInfo&gt; {
    FirebaseUser _user;
    StreamSubscriber _userChnages;
  
    @override
    void initState() { 
      super.initState();
      _userChanges = FirebaseAuth.instance.userChanges().listen((user) {
        setState(() {
          _user = user;
        })
      })
    }
  
  
    @override
    Widget build(BuildContext context) {
      return Container(
         child: Text(_user?.email ?? &quot;No user&quot;),
      );
    }
  }
  </code></pre>
  <p>When I make changes outside the app (for example new user verifies email address or I change their displayName in backend) the stream never fetches those changes and the callback of <code>.listen()</code> is never run.</p>