Repository: flutter
Issue: Autofill Hints iOS: `AutofillHints.newPassword` only recommends once on navigating
Labels: a: text input,platform-ios,framework,f: material design,has reproducible steps,P2,found in release: 2.2,found in release: 2.3,customer: flex,team-text-input,triaged-text-input

## Steps to Reproduce

1. Run on iOS device
2. Tap the `Push create account screen` button
3. Focus on password field
4. iOS new password dialog will show and autofill a safe password
5. Tap on the back button
6. Repeat Step 2-3
7. iOS new password dialog will show, but WILL NOT autofill a safe password

https://user-images.githubusercontent.com/666539/121728912-df5c5f00-cabb-11eb-8d92-4df48d4da4bc.MP4



## MCVE

```dart
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'package:flutter/widgets.dart';

void main() {
  WidgetsFlutterBinding.ensureInitialized();
  runApp(SpikeApp());
}

class SpikeApp extends StatelessWidget {
  const SpikeApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      routes: {
        '/': (_) => _HomeScreen(),
        'create-account': (_) => _CreateAccountScreen(),
      },
    );
  }
}

class _HomeScreen extends StatelessWidget {
  const _HomeScreen({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      body: Center(
        child: Column(
          mainAxisSize: MainAxisSize.min,
          children: [
            ElevatedButton(
              child: Text('Push create account screen'),
              onPressed: () {
                Navigator.of(context).pushNamed('create-account');
              },
            ),
          ],
        ),
      ),
    );
  }
}

class _CreateAccountScreen extends StatefulWidget {
  const _CreateAccountScreen({Key? key}) : super(key: key);

  @override
  __CreateAccountScreenState createState() => __CreateAccountScreenState();
}

class __CreateAccountScreenState extends State<_CreateAccountScreen> {
  final emailController = TextEditingController();
  final passwordController = TextEditingController();

  @override
  Widget build(BuildContext context) {
    final spacer = SizedBox(height: 25);

    return Scaffold(
      appBar: AppBar(
        title: Text('Create account'),
      ),
      body: SafeArea(
        child: Padding(
          padding: const EdgeInsets.all(25),
          child: AutofillGroup(
            child: Column(
              crossAxisAlignment: CrossAxisAlignment.stretch,
              children: [
                Text('Create account'),
                spacer,
                TextField(
                  controller: emailController,
                  autofillHints: [
                    AutofillHints.email,
                  ],
                  textInputAction: TextInputAction.next,
                  decoration: InputDecoration(
                    hintText: 'Your email',
                  ),
                ),
                spacer,
                TextField(
                  controller: passwordController,
                  autofillHints: [
                    AutofillHints.newPassword,
                  ],
                  decoration: InputDecoration(
                    hintText: 'Your password',
                  ),
                ),
                spacer,
                ElevatedButton(
                  child: Text('Save account info'),
                  onPressed: () {
                    TextInput.finishAutofillContext();
                  },
                ),
              ],
            ),
          ),
        ),
      ),
    );
  }
}

```

### flutter doctor
```
Doctor summary (to see all details, run flutter doctor -v):
[✓] Flutter (Channel stable, 2.2.1, on macOS 11.4 20F71 darwin-x64, locale en-US)
[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.2)
[✓] Xcode - develop for iOS and macOS
[✓] Chrome - develop for the web
[✓] Android Studio (version 4.1)
[✓] VS Code (version 1.57.0)
[✓] Connected device (3 available)

• No issues found!
```