Migrate async tests to strong

tests/lib_strong/async/stack_trace13_test.dart

Index: tests/lib_strong/async/stack_trace13_test.dart
diff --git a/tests/lib_strong/async/stack_trace13_test.dart b/tests/lib_strong/async/stack_trace13_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..0b12808dd4af08685b89c3aee1603e97ee9baecd
--- /dev/null
+++ b/tests/lib_strong/async/stack_trace13_test.dart
@@ -0,0 +1,20 @@
+// 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 'package:expect/expect.dart';
+import 'package:async_helper/async_helper.dart';
+import 'dart:async';
+
+main() {
+  StackTrace trace;
+  asyncStart();
+  var f = new Future(() { throw "foo"; });
+  f.then((_) => 499)
+    .then((_) { throw "Unreachable"; },
+      onError: (e, st) {
+        Expect.equals("foo", e);
+        Expect.isNotNull(st);
+        asyncEnd();
+      });
+}