Add mirrors tests

test/codegen/lib/mirrors/inherit_field_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 inherited fields.
+
+library test.inherit_field_test;
+
+import 'dart:mirrors';
+
+import 'stringify.dart';
+
+class Foo {
+  var field;
+}
+
+class Bar extends Foo {
+}
+
+void main() {
+  expect('Variable(s(field) in s(Foo))',
+         reflectClass(Foo).declarations[#field]);
+  expect('<null>',
+         reflectClass(Bar).declarations[#field]);
+}