Migrate async tests to strong

tests/lib_strong/async/stream_take_test.dart

+// Copyright (c) 2016, 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 'dart:async';
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+
+class A { const A(); }
+class B extends A { const B(); }
+
+/// Stream which emits an error if it's not canceled at the correct time.
+///
+/// Must be canceled after at most [maxEvents] events.
+Stream makeStream(int maxEvents) {
+  var c;
+  int event = 0;
+  bool canceled = false;
+  c = new StreamController(onListen: () {
+    new Timer.periodic(const Duration(milliseconds: 10), (t) {
+      if (canceled) {
+        t.cancel();
+        return;
+      }
+      if (event == maxEvents) {
+        c.addError("NOT CANCELED IN TIME: $maxEvents");
+        c.close();
+        t.cancel();
+      } else {
+        c.add(event++);
+      }
+    });
+  }, onCancel: () {
+    canceled = true;
+  });
+  return c.stream;
+}
+
+main() {
+  asyncStart();
+  tests().then((_) { asyncEnd(); });
+}
+
+tests() async {
+  await expectThrowsAsync(makeStream(4).take(5).toList(), "5/4");
+  await expectThrowsAsync(makeStream(0).take(1).toList(), "1/0");
+
+  Expect.listEquals([0, 1, 2, 3, 4], await makeStream(5).take(5).toList());
+
+  Expect.listEquals([0, 1, 2, 3], await makeStream(5).take(4).toList());
+
+  Expect.listEquals([0], await makeStream(5).take(1).toList());
+
+  Expect.listEquals([], await makeStream(5).take(0).toList());
+
+  Expect.listEquals([], await makeStream(0).take(0).toList());
+}
+
+Future expectThrowsAsync(Future computation, String name) {
+  return computation.then((_) {
+    Expect.fail("$name: Did not throw");
+  }, onError: (e, s){});
+}