Add mirrors tests

test/codegen/lib/mirrors/abstract_test.dart

 // 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.
 
+// Test abstract classes are retained.
+
+library test.abstract_test;
+
 import 'dart:mirrors';
 
-main() {
-  print(MirrorSystem.getName(#foo));
+import 'stringify.dart';
+
+abstract class Foo {
 }
+
+void main() {
+  expect('Class(s(Foo) in s(test.abstract_test), top-level)',
+         reflectClass(Foo));
+}