Revert two Kernel changes that were causing test failures.

tests/language_2/async_return_types_test.dart

-// Copyright (c) 2015, 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";
-
-Future foo1() async {
-  return 3;
-}
-
-Future<int> foo2() async {
-  return 3;
-}
-
-Future<int> //# wrongTypeParameter: compile-time error
-foo3() async {
-  return "String";
-}
-
-Future<int, String> //# tooManyTypeParameters: compile-time error
-foo4() async {
-  return "String";
-}
-
-int //# wrongReturnType: compile-time error
-foo5() async {
-  return 3;
-}
-
-Future<int> foo6() async {
-  // This is fine, the future is flattened
-  return new Future<int>.value(3);
-}
-
-Future<Future<int>> //# nestedFuture: compile-time error
-foo7() async {
-  return new Future<int>.value(3);
-}
-
-Iterable<int> foo8() sync* {
-  yield 1;
-  // Can only have valueless return in sync* functions.
-  return
-      8 //# return_value_sync_star: compile-time error
-      ;
-}
-
-Stream<int> foo9() async* {
-  yield 1;
-  // Can only have valueless return in async* functions.
-  return
-      8 //# return_value_sync_star: compile-time error
-      ;
-}
-
-test() async {
-  Expect.equals(3, await foo1());
-  Expect.equals(3, await foo2());
-  Expect.equals("String", await foo3());
-  Expect.equals("String", await foo4());
-  Expect.equals(3, await foo5());
-  Expect.equals(3, await await foo6());
-  Expect.equals(3, await await foo7());
-  Expect.listEquals([1], foo8().toList());
-  Expect.listEquals([1], await foo9().toList());
-}
-
-main() {
-  asyncTest(test);
-}