Repository: flutter
Issue: Flutter DevTools unable to debug Flutter web app in iframe
Labels: c: new feature,a: debugging,platform-web,d: devtools,P3,team-web,triaged-web

### Is there an existing issue for this?

- [X] I have searched the [existing issues](https://github.com/flutter/flutter/issues)
- [X] I have read the [guide to filing a bug](https://flutter.dev/docs/resources/bug-reports)

### Steps to reproduce

- Create a Flutter web app.
- Create an HTML file with an iframe element that points to the Flutter web app.
- Run the Flutter web app in the iframe element.
- Try to debug the Flutter web app using Flutter DevTools or VSCode.


### Expected results

There is currently no official support for debugging Flutter web apps that are running in an iframe. I have a Flutter web app that runs in an iframe of another web app (built with Angular). I need to be able to debug the Flutter web app that's inside the iframe with VSCode (like adding breakpoints) or at least with Dart Devtools. 

So expected: Flutter DevTools should be able to debug the Flutter web app running inside an iframe.

### Actual results

Flutter DevTools are unable to debug the Flutter web app running inside an iframe.

### Code sample

<details><summary>Code sample</summary>

```dart
import 'package:flutter/material.dart';

void main() {
  runApp(const MyApp());
}

class MyApp extends StatelessWidget {
  const MyApp({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        body: Center(
          child: Text('Hello, world!'),
        ),
      ),
    );
  }
}
```

iframe_test.html
```html
<!DOCTYPE html>
<html>
<head>
  <title>Flutter Web App in Iframe</title>
</head>
<body>
  <iframe id="flutter-app" src="http://localhost:4025"></iframe>
</body>
</html>
```
</details>


### Screenshots or Video

_No response_

### Logs

_No response_

### Flutter Doctor output

<details><summary>Doctor output</summary>

```console
[✓] Flutter (Channel stable, 3.10.5, on macOS 13.2.1 22D68 darwin-x64, locale
    en-IN)
    • Flutter version 3.10.5 on channel stable at
      /Users/iamsahilsonawane/Development/flutter
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 796c8ef792 (9 weeks ago), 2023-06-13 15:51:02 -0700
    • Engine revision 45f6e00911
    • Dart version 3.0.5
    • DevTools version 2.23.1

[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.1)
    • Android SDK at /Users/iamsahilsonawane/Library/Android/sdk
    • Platform android-34, build-tools 33.0.1
    • ANDROID_HOME = /Users/iamsahilsonawane/Library/Android/sdk
    • ANDROID_SDK_ROOT = /Users/iamsahilsonawane/Library/Android/sdk
    • Java binary at: /Applications/Android
      Studio.app/Contents/jbr/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build
      17.0.6+0-17.0.6b802.4-9586694)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 14.1)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Build 14B47b
    • CocoaPods version 1.11.3

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 2022.2)
    • Android Studio at /Applications/Android Studio.app/Contents
    • Flutter plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/9212-flutter
    • Dart plugin can be installed from:
      🔨 https://plugins.jetbrains.com/plugin/6351-dart
    • Java version OpenJDK Runtime Environment (build
      17.0.6+0-17.0.6b802.4-9586694)

[✓] VS Code (version 1.81.1)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.70.0

[✓] Connected device (2 available)
    • macOS (desktop) • macos  • darwin-x64     • macOS 13.2.1 22D68 darwin-x64
    • Chrome (web)    • chrome • web-javascript • Google Chrome 115.0.5790.170

[✓] Network resources
    • All expected network resources are available.

• No issues found!
```

</details>