Revert two Kernel changes that were causing test failures.

tests/language_2/async_star_no_cancel_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";
-
-var events = [];
-
-ticker() async* {
-  var sc;
-  var sentTickCount = 0;
-  sc = new StreamController(onListen: () {
-    events.add("listen");
-  }, onCancel: () {
-    events.add("cancel");
-  });
-
-  try {
-    var counter = 0;
-    await for (var tick in sc.stream) {
-      counter++;
-    }
-  } finally {
-    events.add("finally");
-  }
-}
-
-void main() {
-  asyncStart();
-  events.add("main");
-  final subscription = ticker().listen((val) {});
-
-  bool cancelFinished = false;
-  // Cancel the subscription.
-  // The async* function is blocked on an `await` (the inner stream) and won't
-  // be able to complete.
-  Timer.run(() {
-    events.add("invoke cancel");
-    subscription.cancel().then((_) => cancelFinished = true);
-  });
-
-  new Timer(const Duration(milliseconds: 100), () {
-    Expect.isFalse(cancelFinished);
-    Expect.listEquals(["main", "listen", "invoke cancel"], events);
-    asyncEnd();
-  });
-}