Add renames in output when using the mirror helper library.

tests/compiler/dart2js/mirror_helper_unique_minification_test.dart

Index: tests/compiler/dart2js/mirror_helper_unique_minification_test.dart
diff --git a/tests/compiler/dart2js/mirror_helper_unique_minification_test.dart b/tests/compiler/dart2js/mirror_helper_unique_minification_test.dart
index 35885cde245992bd9479c9734e44c7497ff9eda0..972bccd7ae319f073acee09299bc8596d571e244 100644
--- a/tests/compiler/dart2js/mirror_helper_unique_minification_test.dart
+++ b/tests/compiler/dart2js/mirror_helper_unique_minification_test.dart
@@ -33,8 +33,9 @@ void testUniqueMinification() {
   DartBackend backend = compiler.backend;
   Map<Node, String> renames = backend.renames;
 
-  //'Foo' appears twice, so toSet() reduces the length by 1.
-  Expect.equals(renames.values.toSet().length, renames.values.length - 1);
+  //'Foo' appears twice, so toSet() reduces the length by 1,
+  // and the extra code from mirror_helper.dart adds 9 duplicates.
+  Expect.equals(renames.values.toSet().length, renames.values.length - 10);
 }
 
 void testNoUniqueMinification() {