Revert two Kernel changes that were causing test failures.

tests/language_2/async_or_generator_return_type_stacktrace_test.dart

Index: tests/language_2/async_or_generator_return_type_stacktrace_test.dart
diff --git a/tests/language_2/async_or_generator_return_type_stacktrace_test.dart b/tests/language_2/async_or_generator_return_type_stacktrace_test.dart
deleted file mode 100644
index 612cf8b3225469865a30150c9413cfb6388495fe..0000000000000000000000000000000000000000
--- a/tests/language_2/async_or_generator_return_type_stacktrace_test.dart
+++ /dev/null
@@ -1,11 +0,0 @@
-// 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 "package:expect/expect.dart";
-
-void badReturnTypeAsync() async {} // //# 01: compile-time error
-void badReturnTypeAsyncStar() async* {} // //# 02: compile-time error
-void badReturnTypeSyncStar() sync* {} // //# 03: compile-time error
-
-void main() {}