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

lib/unittest/unittest.dart

Index: lib/unittest/unittest.dart
===================================================================
--- lib/unittest/unittest.dart	(revision 10086)
+++ lib/unittest/unittest.dart	(working copy)
@@ -722,6 +722,7 @@
           trace == null ? '' : trace.toString());
     }
   }
+  _nextTestCase();

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

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);
  });
}

 }
 
 /**