Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/generic_local_function_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_function_typedef;
 
+@MirrorsUsed(targets: "test.generic_function_typedef")
 import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 
 import 'generics_helper.dart';
 
 class C<T> {
   makeClosure1() {
     T closure1(T t) {}
     return closure1;
@@ skipping 10 matching lines @@
 
 main() {
   ClosureMirror closure1 = reflect(new C<String>().makeClosure1());
   Expect.equals(reflectClass(String), closure1.function.returnType);
   Expect.equals(reflectClass(String), closure1.function.parameters[0].type);
 
   ClosureMirror closure2 = reflect(new C<String>().makeClosure2());
   Expect.equals(reflectClass(String), closure2.function.returnType);
   Expect.equals(reflectClass(String), closure2.function.parameters[0].type);
 }