Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/generic_mixin_applications_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_mixin_applications;
 
+@MirrorsUsed(targets: "test.generic_mixin_applications")
 import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 
 import 'generics_helper.dart';
 
 class Super<S> {}
 class Mixin<M> {}
 class Nixim<N> {}
 
@@ skipping 70 matching lines @@
   typeArguments(reflect(new NonGenericClass2()).type, []);
   typeArguments(reflect(new GenericClass1<bool>()).type, [reflectClass(bool)]);
   typeArguments(reflect(new GenericClass2<bool>()).type, [reflectClass(bool)]);
   typeArguments(reflect(new GenericMultipleMixins<bool, String, int>()).type, [reflectClass(bool), reflectClass(String), reflectClass(int)]);
   // Anonymous mixin applications have no type parameters or type arguments.
   typeArguments(reflect(new NonGenericClass1()).type.superclass, []);
   typeArguments(reflect(new NonGenericClass2()).type.superclass, []);
   typeArguments(reflect(new GenericClass1<bool>()).type.superclass, []);
   typeArguments(reflect(new GenericClass2<bool>()).type.superclass, []);
 }