Repository: flutter
Issue: flutter test --coverage --platform=chrome exits unexpectedly 
Labels: tool,platform-web,P3,team-web,triaged-web

I was trying to get test coverage generated by running this command:
`flutter test --coverage --no-test-assets --platform chrome --verbose`

```
07:14 +281 ~2: All tests passed!                                                                                                       
[+1636 ms] coverage information collection complete
[  +20 ms] "flutter test" took 4,76,458ms.

#0      throwToolExit (package:flutter_tools/src/base/common.dart:14:3)
#1      TestCommand.runCommand (package:flutter_tools/src/commands/test.dart:275:9)
<asynchronous suspension>
#2      FlutterCommand.verifyThenRunCommand (package:flutter_tools/src/runner/flutter_command.dart:722:18)
#3      _rootRunUnary (dart:async/zone.dart:1192:38)
#4      _CustomZone.runUnary (dart:async/zone.dart:1085:19)
#5      _FutureListener.handleValue (dart:async/future_impl.dart:141:18)
#6      Future._propagateToListeners.handleValueCallback (dart:async/future_impl.dart:682:45)
#7      Future._propagateToListeners (dart:async/future_impl.dart:711:32)
#8      Future._completeWithValue (dart:async/future_impl.dart:526:5)
#9      Future._asyncComplete.<anonymous closure> (dart:async/future_impl.dart:556:7)
#10     _rootRun (dart:async/zone.dart:1184:13)
#11     _CustomZone.run (dart:async/zone.dart:1077:19)
#12     _CustomZone.runGuarded (dart:async/zone.dart:979:7)
#13     _CustomZone.bindCallbackGuarded.<anonymous closure> (dart:async/zone.dart:1019:23)
#14     _microtaskLoop (dart:async/schedule_microtask.dart:43:21)
#15     _startMicrotaskLoop (dart:async/schedule_microtask.dart:52:5)
#16     _runPendingImmediateCallback (dart:isolate-patch/isolate_patch.dart:118:13)
#17     _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:169:5)
```

Ouput of `flutter doctor -v`

```
Downloading android-arm-profile/darwin-x64 tools...                 1.1s
Downloading android-arm-release/darwin-x64 tools...                 0.8s
Downloading android-arm64-profile/darwin-x64 tools...               1.1s
Downloading android-arm64-release/darwin-x64 tools...               1.0s
Downloading android-x64-profile/darwin-x64 tools...                 0.7s
Downloading android-x64-release/darwin-x64 tools...                 0.9s
[✓] Flutter (Channel beta, v1.17.0, on Mac OS X 10.14.6 18G1012, locale en-IN)
    • Flutter version 1.17.0 at /Users/gogol/Documents/Flutter/flutter
    • Framework revision d3ed9ec945 (2 weeks ago), 2020-04-06 14:07:34 -0700
    • Engine revision c9506cb8e9
    • Dart version 2.8.0 (build 2.8.0-dev.18.0 eea9717938)

[✗] Android toolchain - develop for Android devices
    ✗ Unable to locate Android SDK.
      Install Android Studio from: https://developer.android.com/studio/index.html
      On first launch it will assist you in installing the Android SDK components.
      (or visit https://flutter.dev/docs/get-started/install/macos#android-setup for detailed instructions).
      If the Android SDK has been installed to a custom location, set ANDROID_SDK_ROOT to that location.
      You may also want to add it to your PATH environment variable.


 
[!] Xcode - develop for iOS and macOS (Xcode 10.3)
    • Xcode at /Applications/Xcode.app/Contents/Developer
    • Xcode 10.3, Build version 10G8
    ✗ Flutter requires a minimum Xcode version of 11.0.0.
      Download the latest version or update via the Mac App Store.
    • CocoaPods version 1.8.4

[✓] Chrome - develop for the web
    • Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[!] Android Studio (not installed)
    • Android Studio not found; download from https://developer.android.com/studio/index.html
      (or visit https://flutter.dev/docs/get-started/install/macos#android-setup for detailed instructions).

[✓] VS Code (version 1.44.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.9.1

[✓] Connected device (2 available)
    • Chrome     • chrome     • web-javascript • Google Chrome 81.0.4044.113
    • Web Server • web-server • web-javascript • Flutter Tools
```