Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/invoke_closurization2_test.dart

 // Copyright (c) 2014, 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.invoke_closurization_test;
 
+@MirrorsUsed(targets: "test.invoke_closurization_test")
 import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 
 class A {
   foo() => "foo";
   bar([x]) => "bar-$x";
   gee({named}) => "gee-$named";
 
   // Methods that must be intercepted.
@@ skipping 104 matching lines @@
   Expect.equals("indexOf-499", f.invoke(#call, [499], {}).reflectee);
   f = getAMirror().getField(#matchAsPrefix);
   Expect.equals("matchAsPrefix-FOO,BAR",
                 f.invoke(#call, ["FOO", "BAR"]).reflectee);
   f = getAMirror().getField(#toList);
   Expect.equals("toList-1",
                 f.invoke(#call, [], {#growable: 1}).reflectee);
   f = getAMirror().getField(#toSet);
   Expect.equals("toSet-true", f.invoke(#call, [], {#named: true}).reflectee);
 }