Migrate block 163 to Dart 2.0.

tests/language/vm/async_await_catch_stacktrace_test.dart

-// Copyright (c) 2017, 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";
-
-void main() {
-  x() async {
-    print("Starting!");
-    try {
-      await runAsync();
-    } catch (e, st) {
-      print("Got exception and stacktrace:");
-      var stText = st.toString();
-      print(e);
-      print(stText);
-      // Stacktrace should be something like
-      // #0      runAsync.<runAsync_async_body> (this file)
-      // #1      Future.Future.microtask.<anonymous closure> (dart:async/future.dart:184)
-      // #2      _microtaskLoop (dart:async/schedule_microtask.dart:41)
-      // #3      _startMicrotaskLoop (dart:async/schedule_microtask.dart:50)
-      // #4      _runPendingImmediateCallback (dart:isolate-patch/isolate_patch.dart:96)
-      // #5      _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:149)
-
-      // if exception and stacktrace is rethrown correctly, NOT
-
-      // #0      main.<anonymous closure>.async_op (this file)
-      // #1      _asyncErrorWrapperHelper.<anonymous closure> (dart:async:134:33)
-      // #2      _RootZone.runBinary (dart:async/zone.dart:1410:54)
-      // #3      _FutureListener.handleError (dart:async/future_impl.dart:146:20)
-      // #4      _Future._propagateToListeners.handleError (dart:async/future_impl.dart:649:47)
-      // #5      _Future._propagateToListeners (dart:async/future_impl.dart:671:13)
-      // #6      _Future._completeError (dart:async/future_impl.dart:485:5)
-      // #7      _SyncCompleter._completeError (dart:async/future_impl.dart:56:12)
-      // #8      _Completer.completeError (dart:async/future_impl.dart:27:5)
-      // #9      runAsync.async_op (this file)
-      // #10     Future.Future.microtask.<anonymous closure> (dart:async/future.dart:184:26)
-      // #11     _microtaskLoop (dart:async/schedule_microtask.dart:41:5)
-      // #12     _startMicrotaskLoop (dart:async/schedule_microtask.dart:50:5)
-      // #13     _runPendingImmediateCallback (dart:isolate:1054:5)
-      // #14     _RawReceivePortImpl._handleMessage (dart:isolate:1104:5)
-
-      Expect.isFalse(stText.contains("propagateToListeners"));
-      Expect.isFalse(stText.contains("_completeError"));
-    }
-    print("Ending!");
-  }
-
-  asyncStart();
-  x().then((_) => asyncEnd());
-}
-
-runAsync() async {
-  throw 'oh no!';
-}