Repository: flutter
Issue: Navigating to Screen which is not  wrapped by Scaffold causes laggy on iOS
Labels: platform-ios,framework,f: material design,c: performance,f: routes,has reproducible steps,found in release: 2.8,found in release: 2.9,team-design,triaged-design

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## Steps to Reproduce

<!-- Please include full steps to reproduce so that we can reproduce the problem. -->

1. Screen A navigate to Screen B
2. Screen B returns a widget without being wrapped by Scaffold widget (ex CircularProgressIndicator) 

**Expected results:** <!-- what did you want to see? -->

Navigating should be smooth

![Simulator Screen Recording - iPhone 7 - 2022-01-24 at 07 49 50](https://user-images.githubusercontent.com/28992487/150706314-83491450-af61-4d89-b788-8a7ada99fd10.gif)

**Actual results:** <!-- what did you see? -->

It's laggy here

![Simulator Screen Recording - iPhone 7 - 2022-01-24 at 07 50 56](https://user-images.githubusercontent.com/28992487/150706300-b04ca379-7d84-4d92-bae2-1aa0599aaed6.gif)


<details>
<summary>Code sample</summary>

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```dart

class ScreenA extends StatelessWidget {
  const ScreenA({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return Scaffold(floatingActionButton: FloatingActionButton(
      onPressed: () {
        Navigator.push(
            context, MaterialPageRoute(builder: (context) => const ScreenB()));
      },
    ));
  }
}


class ScreenB extends StatelessWidget {
  const B({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return const Center(child: CircularProgressIndicator());
  }
}


```

</details>

<details>
  <summary>Logs</summary>

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```
```

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     Run `flutter analyze` and attach any output of that command below.
     If there are any analysis errors, try resolving them before filing this issue.
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```
```

<!-- Finally, paste the output of running `flutter doctor -v` here. -->

```
Doctor summary (to see all details,
run flutter doctor -v):
[✓] Flutter (Channel stable, 2.8.1, on
    macOS 12.0.1 21A559 darwin-x64,
    locale en-US)
[✓] Android toolchain - develop for
    Android devices (Android SDK
    version 32.0.0)
[✓] Xcode - develop for iOS and macOS
    (Xcode 13.2.1)
[✓] Chrome - develop for the web
[✓] Android Studio (version 2020.3)
[✓] VS Code (version 1.63.2)
[✓] Connected device (2 available)

• No issues found!
```

</details>


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