accept null type casts in dummy noSuchMethod checks

tests/compiler/dart2js/no_such_method_enabled_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';
 import 'compiler_helper.dart';
 
 Future dummyImplTest() async {
@@ skipping 253 matching lines @@
   Expect.isTrue(compiler.backend.enabledNoSuchMethod);
   ClassElement clsA = findElement(compiler, 'A');
   Expect.isTrue(
       compiler.backend.noSuchMethodRegistry.otherImpls.contains(
           clsA.lookupMember('noSuchMethod')));
   Expect.isTrue(
       compiler.backend.noSuchMethodRegistry.complexReturningImpls.contains(
           clsA.lookupMember('noSuchMethod')));
 }
 
+Future dummyImplTest13() async {
+  String source = """
+class A {
+  noSuchMethod(x) => super.noSuchMethod(x) as dynamic;
+}
+main() {
+  print(new A().foo());
+}
+""";
+  Uri uri = new Uri(scheme: 'source');
+  var compiler = compilerFor(source, uri);
+  await compiler.run(uri);
+  Expect.isFalse(compiler.backend.enabledNoSuchMethod);
+  ClassElement clsA = findElement(compiler, 'A');
+  Expect.isTrue(
+      compiler.backend.noSuchMethodRegistry.defaultImpls.contains(
+          clsA.lookupMember('noSuchMethod')));
+}
+
 main() {
   asyncTest(() async {
     await dummyImplTest();
     await dummyImplTest2();
     await dummyImplTest3();
     await dummyImplTest4();
     await dummyImplTest5();
     await dummyImplTest6();
     await dummyImplTest7();
     await dummyImplTest8();
     await dummyImplTest9();
     await dummyImplTest10();
     await dummyImplTest11();
     await dummyImplTest12();
+    await dummyImplTest13();
   });
 }