title: Reauthenticate user with Facebook
body: <p>I am using Flutter to create a mobile application. I am using Firebase for authentication. My user logs in with Facebook.  The user should reauthenticate him/her self when deleting the account.  The documentation talks about reauthentication using email and password like this:</p>
  <pre><code>// Create a credential
  EmailAuthCredential credential = EmailAuthProvider.credential(email: email, password: password);
  
  // Reauthenticate
  await FirebaseAuth.instance.currentUser.reauthenticateWithCredential(credential);
  </code></pre>
  <p>Since the user does not have an email and password but rather he is logged in with Facebook, I should reauthenticate the user with Facebook.  I searched the documentation for this but I had no luck.</p>
  <p>Could some one be kind and tell me how to do that.</p>
  <p>I tried to log the user in with Facebook (even though he is already logged in) but was not successful.  Her is what I tried:</p>
  <pre><code>FacebookLoginResult result = await FacebookLogin().logIn(permissions: [
    FacebookPermission.publicProfile,
    FacebookPermission.email,
  ]);
  
  switch (result.status) {
    case FacebookLoginStatus.success:
      FacebookAccessToken? accessToken = result.accessToken;
      if (accessToken == null) {
        return null;
      }
  
      UserCredential userCredential = await _auth.signInWithCredential(
        FacebookAuthProvider.credential(accessToken.token),
      );
      return userCredential;
  
    case FacebookLoginStatus.cancel:
      throw FirebaseAuthException(
        code: 'ERROR_FACEBOOK_LOGIN_FAILED',
        message: result.error?.developerMessage,
      );
    default:
      throw UnimplementedError();
  }
  
  await FirebaseAuth.instance.currentUser?.reauthenticateWithCredential(
    userCredential!.credential!,
  );
  </code></pre>