Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/generic_f_bounded_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.generic_f_bounded;
 
+@MirrorsUsed(targets: "test.generic_f_bounded")
 import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 
 import 'generics_helper.dart';
 
 class Magnitude<T> {}
 class Real extends Magnitude<Real> {}
 class Sorter<R extends Magnitude<R>> {}
 class RealSorter extends Sorter<Real> {}
@@ skipping 32 matching lines @@
   typeParameters(magnitudeOfR, [#T]);
 
   typeArguments(magnitudeDecl, []);
   typeArguments(realDecl, []);
   typeArguments(sorterDecl, []);
   typeArguments(realSorterDecl, []);
   typeArguments(magnitudeOfReal, [realDecl]); /// 01: ok
   typeArguments(sorterOfReal, [realDecl]); /// 01: ok
   typeArguments(magnitudeOfR, [rFromSorter]);
 }