Repository: flutter
Issue: [web] --host-vmservice-port is not working on web plarform
Labels: tool,platform-web,P2,team-web,triaged-web

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## Steps to Reproduce
Context:
- I am using Flutter Driver to write integration test and I need to define a specify port to easily testing, because I want to use a driver drive multiple apps, but --host-vmservice-port is not working on the web, app is ok.
<!-- You must include full steps to reproduce so that we can reproduce the problem. -->

1. Run `flutter run -d chrome --web-renderer html --host-vmservice-port=8001 --disable-service-auth-codes`.

**Expected results:** <!-- what did you want to see? -->
`Launching lib/main.dart on Chrome in debug mode...
Waiting for connection from debug service on Chrome...             56.0s
This app is linked to the debug service: http://127.0.0.1:8001/
Debug service listening on http://127.0.0.1:8001/`

**Actual results:** <!-- what did you see? -->
`Launching lib/main.dart on Chrome in debug mode...
Waiting for connection from debug service on Chrome...             56.0s
This app is linked to the debug service: ws://127.0.0.1:63757/uP5WdUpWmto=/ws
Debug service listening on ws://127.0.0.1:63757/uP5WdUpWmto=/ws`

<details>
  <summary>Logs</summary>

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```
[✓] Flutter (Channel stable, 2.2.0, on macOS 11.2.3 20D91 darwin-x64, locale en-VN)
    • Flutter version 2.2.0 at /Users/phamnhuvu/Downloads/flutter
    • Framework revision b22742018b (3 weeks ago), 2021-05-14 19:12:57 -0700
    • Engine revision a9d88a4d18
    • Dart version 2.13.0

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.3)
    • Android SDK at /Users/phamnhuvu/Library/Android/sdk
    • Platform android-30, build-tools 30.0.3
    • Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
    • Java version OpenJDK Runtime Environment (build 11.0.8+10-b944.6916264)
    • All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 12.5, Build version 12E262
    • CocoaPods version 1.10.1

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 4.2)
    • 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 11.0.8+10-b944.6916264)

[✓] VS Code (version 1.56.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.23.0

[✓] Connected device (2 available)
    • sdk gphone x86 (mobile) • emulator-5554 • android-x86    • Android 11 (API 30) (emulator)
    • Chrome (web)            • chrome        • web-javascript • Google Chrome 91.0.4472.77

• No issues found!
```

</details>