Add mirrors tests

test/codegen/lib/mirrors/generic_list_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.
+
+library test.superclass;
+
+import 'dart:mirrors';
+import 'package:expect/expect.dart';
+
+class Foo<T> {
+  List<T> makeList() {
+    if (new DateTime.now().millisecondsSinceEpoch == 42) return [];
+    return new List<T>();
+  }
+}
+
+main() {
+  List<String> list = new Foo<String>().makeList();
+  var cls = reflectClass(list.runtimeType);
+  Expect.isNotNull(cls, 'Failed to reflect on MyClass.');
+}