Add renames in output when using the mirror helper library.

tests/utils/dummy_compiler_test.dart

Index: tests/utils/dummy_compiler_test.dart
diff --git a/tests/utils/dummy_compiler_test.dart b/tests/utils/dummy_compiler_test.dart
index f95a289ea92ae79a27cecd63c972e597e4bbc58d..5c7c1dae6b6cf346039935d9de223d764c6d0ff1 100644
--- a/tests/utils/dummy_compiler_test.dart
+++ b/tests/utils/dummy_compiler_test.dart
@@ -85,7 +85,7 @@ var mapTypeToInterceptor;""";
     } else if (uri.path.endsWith('isolate_helper.dart')) {
       source = 'library isolatehelper; class _WorkerStub {}';
     } else {
-      source = "library lib;";
+      source = "library lib${uri.path.replaceAll('/', '.')};";
     }
   } else {
    throw "unexpected URI $uri";