Migrate async tests to strong

tests/lib_strong/async/catch_errors21_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 'package:async_helper/async_helper.dart';
+import "package:expect/expect.dart";
+import 'dart:async';
+import 'catch_errors.dart';
+
+main() {
+  asyncStart();
+  Completer done = new Completer();
+
+  var events = [];
+  var controller = new StreamController();
+  // Test that stream errors, as a result of bad user-code (`map`) are correctly
+  // caught by `catchErrors`. Note that the values are added outside both
+  // `catchErrors`, but since the `listen` happens in the most nested
+  // `catchErrors` it is caught there.
+  catchErrors(() {
+    catchErrors(() {
+      controller.stream.map((x) { throw x; }).listen((x) {
+        // Should not happen.
+        events.add("bad: $x");
+      });
+    }).listen((x) {
+                events.add("caught: $x");
+                if (x == 4) done.complete(true);
+              },
+              onDone: () { Expect.fail("Unexpected callback"); });
+  }).listen((x) { events.add("outer: $x"); },
+            onDone: () { Expect.fail("Unexpected callback"); });
+
+  done.future.whenComplete(() {
+    // Give handlers time to run.
+    Timer.run(() {
+      Expect.listEquals(["caught: 1",
+                          "caught: 2",
+                          "caught: 3",
+                          "caught: 4",
+                        ],
+                        events);
+      asyncEnd();
+    });
+  });
+
+  [1, 2, 3, 4].forEach(controller.add);
+  controller.close();
+}