anchor.diff:                                  leading: const Icon(Icons.account_box),
                                   title: new Text('Sign in with google'),
                                   onTap: () {
  -                                  _signInWithGoogle().then((account) {
  -                                    _rebuild();
  +                                  _signIn().then((success) {
  +                                    if (success) {
  +                                      _rebuild();
  +                                    }
                                     });
                                   },
                                 )
  
positive.code: import 'package:flutter/material.dart';
  import 'package:google_sign_in/google_sign_in.dart';
  
  final FirebaseAuth _auth = FirebaseAuth.instance;
  final GoogleSignIn _googleSignIn = new GoogleSignIn();
  
  class AccountDrawer extends StatefulWidget {
  
negative.code:   Animation<double> _drawerContentsOpacity;
    Animation<Offset> _drawerDetailsPosition;
  
    Future<bool> _signIn({bool onlySilently = false}) async {
      final googleUser = await _signInWithGoogle(onlySilently);
  
      if (googleUser != null) {
        final firebaseUser = await _signInToFirebase();
        return firebaseUser != null;
      }
  
      return false;
    }
  
    Future<GoogleSignInAccount> _signInWithGoogle(bool onlySilently) async {
      var googleUser = _googleSignIn.currentUser;
  
      if (googleUser == null) {
        googleUser = await _googleSignIn.signInSilently();
      }
  
      if (!onlySilently && googleUser == null) {
        googleUser = await _googleSignIn.signIn();
      }
  
      return googleUser;
    }
  
    Future<FirebaseUser> _signInToFirebase() async {
      var googleUser = _googleSignIn.currentUser;
  
      if (googleUser == null) {
        return null;
      }
  
      final GoogleSignInAuthentication googleAuth =
          await googleUser.authentication;
      final FirebaseUser firebaseUser = await _firebaseAuth.signInWithGoogle(
        accessToken: googleAuth.accessToken,
        idToken: googleAuth.idToken,
      );
  
      return firebaseUser;
    }
  
    void _rebuild() {
  