Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/static_members_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.static_members;
 
+@MirrorsUsed(targets: "test.static_members")
 import 'dart:mirrors';
 import 'package:expect/expect.dart';
 
 import 'stringify.dart';
 import 'declarations_model.dart' as declarations_model;
 
 selectKeys(map, predicate) {
   return map.keys.where((key) => predicate(map[key]));
 }
 
@@ skipping 15 matching lines @@
      ],
     selectKeys(cm.staticMembers, (dm) => true));
 
   Expect.setEquals(
     [#staticVariable,
      const Symbol('staticVariable='),
      MirrorSystem.getSymbol('_staticVariable', lm),
      MirrorSystem.getSymbol('_staticVariable=', lm)],
     selectKeys(cm.staticMembers, (dm) => dm.isSynthetic));
 }