Revert "Support runtime check of function types."

tests/language/function_subtype_null.dart

Index: tests/language/function_subtype_null.dart
diff --git a/tests/language/function_subtype_null.dart b/tests/language/function_subtype_null.dart
deleted file mode 100644
index c235b81928865a5a89e481b63d6a987edef40b19..0000000000000000000000000000000000000000
--- a/tests/language/function_subtype_null.dart
+++ /dev/null
@@ -1,17 +0,0 @@
-// Copyright (c) 2013, 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.
-// Dart test program for constructors and initializers.
-
-// Check function subtyping for null.
-
-import 'package:expect/expect.dart';
-
-typedef int Foo(bool a, [String b]);
-typedef int Bar<T>(T a, [String b]);
-
-main() {
-  Expect.isFalse(null is Foo, 'null is Foo');
-  Expect.isFalse(null is Bar<bool>, 'null is Bar<bool>');
-  Expect.isFalse(null is Bar, 'null is Bar');
-}