Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/reflect_model_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.reflect_model_test;
 
+@MirrorsUsed(targets: "test.reflect_model_test")
 import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 
 import 'model.dart';
 import 'stringify.dart';
 
 isNoSuchMethodError(e) => e is NoSuchMethodError;
 
 variablesOf(ClassMirror cm) {
@@ skipping 115 matching lines @@
   Expect.equals('aMethod', c.invoke(aMethod, []).reflectee);
 
   Expect.throws(() { a.invoke(bMethod, []); }, isNoSuchMethodError);
   Expect.equals('bMethod', b.invoke(bMethod, []).reflectee);
   Expect.equals('bMethod', c.invoke(bMethod, []).reflectee);
 
   Expect.throws(() { a.invoke(cMethod, []); }, isNoSuchMethodError);
   Expect.throws(() { b.invoke(cMethod, []); }, isNoSuchMethodError);
   Expect.equals('cMethod', c.invoke(cMethod, []).reflectee);
 }