js_util promiseToFuture async tests not waiting for completion on d8

[rileyporter]

When running an async test on d8 for the js_util.promiseToFuture method, the test runner seems to be completing before waiting for the async tests to finish.

Test for small repro:

import 'dart:async';

import 'package:js/js.dart';
import 'package:js/js_util.dart' as js_util;
import 'package:expect/minitest.dart';
import 'package:async_helper/async_helper.dart';

@JS()
external void eval(String code);

@JS()
abstract class Promise<T> {}

@JS()
external Promise get p;

main() {
  eval(r""" var p = new Promise(resolve => resolve('resolved'));""");

  Future<void> testResolvedPromise() async {
    final String result = await js_util.promiseToFuture(p);
    expect(result, equals('resolved'));
    print('error: never reached'); // debugging print not reached
  }

  asyncTest(() async {
    await testResolvedPromise();
  });
}

This passes on chrome configurations, but with d8 it doesn't await the resolved Promise before finishing the test. The print debugging statement is never reached before the test runner completes. Instead this error is printed:

exit code:
0

stdout:
unittest-suite-wait-for-done

Deobfuscated error and stack:
<no error message found>
    at unittest-suite-wait-for-done unparsed


--- Re-run this test:
python tools/test.py -n dart2js-production-mac-d8 tests/lib/js/js_util/async_test.dart
[00:02 | 100% | +    0 | -    1]

CL with async_test for tracking context: https://dart-review.googlesource.com/c/sdk/+/185281/2/tests/lib/js/js_util/async_test.dart The async test already existed under tests/lib/html, but was skipped for d8 configurations due to reliance on dart html.

The solution may be to update our async test to force d8 to wait manually or to figure out a way to get hooks into the Promise to know when it has completed and get d8 to listen to that signal.