Migrate async tests to strong

tests/lib_strong/async/catch_errors12_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 = [];
+  // Tests that errors that have been delayed by several milliseconds with
+  // Timers are still caught by `catchErrors`.
+  catchErrors(() {
+    events.add("catch error entry");
+    Timer.run(() { throw "timer error"; });
+    new Timer(const Duration(milliseconds: 100), () { throw "timer2 error"; });
+    new Future.value(499).then((x) {
+      new Timer(const Duration(milliseconds: 200), () {
+        done.complete(499);
+        throw x;
+      });
+    });
+    throw "catch error";
+  }).listen((x) {
+      events.add(x);
+    },
+    onDone: () { Expect.fail("Unexpected callback"); });
+  done.future.whenComplete(() {
+    // Give time to execute the callbacks.
+    Timer.run(() {
+      Expect.listEquals([
+            "catch error entry",
+            "main exit",
+            "catch error",
+            "timer error",
+            "timer2 error",
+            499,
+          ],
+          events);
+      asyncEnd();
+    });
+  });
+  events.add("main exit");
+}