Add @MirrorsUsed annotations to speed up tests.

tests/lib/mirrors/fake_function_with_call_test.dart

Index: tests/lib/mirrors/fake_function_with_call_test.dart
diff --git a/tests/lib/mirrors/fake_function_with_call_test.dart b/tests/lib/mirrors/fake_function_with_call_test.dart
index 05523ef8be736a3222df2557f31b3509114fb6a4..fb0a83166b0f596595c0ff80b9744ee78144a415 100644
--- a/tests/lib/mirrors/fake_function_with_call_test.dart
+++ b/tests/lib/mirrors/fake_function_with_call_test.dart
@@ -2,6 +2,9 @@
 // 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 lib;
+
+@MirrorsUsed(targets: "lib")
 import "dart:mirrors";
 
 import "package:expect/expect.dart";