Add mirrors tests

test/codegen/lib/mirrors/local_isolate_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 the local IsolateMirror.
+
+library test.local_isolate_test;
+
+import 'dart:mirrors';
+
+import 'package:expect/expect.dart';
+
+class Foo {}
+
+void main() {
+  LibraryMirror rootLibrary = reflectClass(Foo).owner;
+  IsolateMirror isolate = currentMirrorSystem().isolate;
+  Expect.isTrue(isolate.debugName is String);
+  Expect.isTrue(isolate.isCurrent);
+  Expect.equals(rootLibrary, isolate.rootLibrary);
+}