Migrate async tests to strong

tests/lib_strong/async/catch_errors4_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 = [];
+  // Test that synchronous errors inside a `catchErrors` are caught.
+  catchErrors(() {
+    events.add("catch error entry");
+    throw "catch error";
+  }).listen((x) {
+      events.add(x);
+      done.complete(true);
+    },
+    onDone: () { Expect.fail("Unexpected callback"); });
+
+  done.future.whenComplete(() {
+    Expect.listEquals(["catch error entry",
+                        "main exit",
+                        "catch error",
+                        ],
+                        events);
+    asyncEnd();
+  });
+  events.add("main exit");
+}