Add mirrors tests

test/codegen/lib/mirrors/invocation_cache_test.dart

 // Copyright (c) 2014, 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.
 
-// SharedOptions=--enable-enum
-
+@MirrorsUsed(targets: const ["A"])
 import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 
-enum Foo { BAR, BAZ }
+class A {
+  toString() => "A";
+}
 
 main() {
-  Expect.equals('Foo.BAR', Foo.BAR.toString());
-  var name = reflect(Foo.BAR).invoke(#toString, []).reflectee;
-  Expect.equals('Foo.BAR', name);
+  // The invocation cache must not find the 'toString' from JavaScript's
+  // Object.prototype.
+  var toString = reflect(new A()).getField(#toString).reflectee;
+  Expect.equals("A", Function.apply(toString, [], {}));
 }