Fix issue 4227 - unittest.dart silently consumes exceptions when expectAsync is active.

Fix issue 4227 - unittest.dart silently consumes exceptions when expectAsync is active.
Committed: https://code.google.com/p/dart/source/detail?r=10103

[Siggi Cherem (dart-lang), 2012-08-01 00:11:16]

http://codereview.chromium.org/10834098/diff/2001/lib/unittest/unittest.dart
File lib/unittest/unittest.dart (right):

http://codereview.chromium.org/10834098/diff/2001/lib/unittest/unittest.dart#...
lib/unittest/unittest.dart:725: _nextTestCase();
I'm thinking more about this, and I don't know if this is entirely correct - for
example, if we have 2 async tests one after another, this will possibly advance
to a later test that is not related to where the failure happened:

#library('foo_test');
#import('dart:html');
#import('../../../lib/unittest/unittest.dart');
#import('../../../lib/unittest/html_config.dart');

void main() {
  useHtmlConfiguration();
  test('one', () {
    var f = expectAsync0(() {});
    window.setTimeout(() => expect(false), 0);

    // 'two' will be marked as failed because of this
    window.setTimeout(() => expect(false), 0);
  });

  test('two', () {
    window.setTimeout(expectAsync0(() {}), 60);
  });
}

[Siggi Cherem (dart-lang), 2012-08-01 00:45:43]

lgtm. Good point, I am not sure if we already had the problem.

I think the problem can be solved, though. We would need to keep track on
guardAsync which test it is being guarded. In that sense, it should only mark as
failing that test (and not look at the 'current' test).