Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/static_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 static members.
 
+library lib;
+
+@MirrorsUsed(targets: "lib")
 import 'dart:mirrors';
 
 import 'stringify.dart';
 
 class Foo {
   static String bar = '...';
   String aux = '';
   static foo() {}
   baz() {}
 }
 
 void main() {
   expect('Variable(s(aux) in s(Foo))',
          reflectClass(Foo).declarations[new Symbol('aux')]);
   expect('Method(s(baz) in s(Foo))',
          reflectClass(Foo).declarations[new Symbol('baz')]);
   expect('<null>',
          reflectClass(Foo).declarations[new Symbol('aux=')]);
   expect('Method(s(foo) in s(Foo), static)',
          reflectClass(Foo).declarations[new Symbol('foo')]);
   expect('Variable(s(bar) in s(Foo), static)',
          reflectClass(Foo).declarations[new Symbol('bar')]);
 }