Migrated test block 168 to Dart 2.0.

tests/lib/async/dart2js_uncaught_error_test.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-import "dart:async";
-import "dart:js";
-import "dart:collection" show Queue;
-import "package:expect/expect.dart";
-import "package:async_helper/async_helper.dart";
-
-var errors = new Queue();
-int ctr = 0;
-
-main() {
-  print("STARTED");
-  asyncStart();
-
-  void errorHandler(self, message, url, line, [column, error]) {
-    print(">> $message / $ctr");
-    var expect = errors.removeFirst();
-    if (ctr == 2) {
-      asyncEnd();
-      print("DONE");
-    }
-    Expect.equals(expect[0].toString(), message);
-    Expect.equals(expect[1].toString(), error["stack"].toString());
-  }
-
-  context["onerror"] = new JsFunction.withThis(errorHandler);
-
-  void throwit() {
-    var err = ++ctr;
-    try {
-      throw err;
-    } catch (e, s) {
-      errors.add([e, s]);
-      rethrow;
-    }
-  }
-
-  () async {
-    () async {
-      throwit();
-    }();
-    throwit();
-  }();
-}