Migrate async tests to strong

tests/lib_strong/async/catch_errors7_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 asynchronous errors are caught.
+  catchErrors(() {
+    events.add("catch error entry");
+    var futures = [
+      new Future.error("future error"),
+      new Future.error("future error2"),
+      new Future.value(499).then((x) => throw x),
+    ];
+    int completedCount = 0;
+    for (var future in futures) {
+      future.whenComplete(() {
+        completedCount++;
+        if (completedCount == 3) done.complete(true);
+      });
+    }
+    throw "catch error";
+  }).listen((x) {
+      events.add(x);
+    },
+    onDone: () { Expect.fail("Unexpected callback"); });
+
+  done.future.whenComplete(() {
+    // Give handlers time to execute.
+    Timer.run(() {
+      Expect.listEquals(
+          ["catch error entry",
+            "main exit",
+            "catch error",
+            "future error",
+            "future error2",
+            499,
+          ],
+          events);
+      asyncEnd();
+    });
+  });
+  events.add("main exit");
+}