Revert two Kernel changes that were causing test failures.

tests/language_2/async_call_test.dart

-// Copyright (c) 2017, 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";
-
-var result = "";
-
-foo() {
-  result += "foo";
-}
-
-bar() async {
-  result += "bar";
-}
-
-main() async {
-  var f = new Future(foo);
-  var b = bar();
-  Expect.equals("", result);
-  scheduleMicrotask(() => result += "micro");
-  await b;
-  await f;
-
-  // Validates that bar is scheduled as a microtask, before foo.
-  Expect.equals("barmicrofoo", result);
-}