Add mirrors tests

test/codegen/lib/mirrors/library_metatarget_test_annotations_lib.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 compiler_annotations;
+// Regression test for the combined use of metatargets and library tags.
 
-// This library contains annotations useful for testing.
+library annotations;
 
-// TODO(ngeoffray): Implement in dart2js.
-class DontInline {
-  const DontInline();
+class UsedOnlyOnLibrary {
+  const UsedOnlyOnLibrary();
 }
+const usedOnlyOnLibrary = const UsedOnlyOnLibrary();
+
+class Reflectable {
+  const Reflectable();
+}
+const Reflectable reflectable = const Reflectable();