Fix name of libraries without a library declaration to be the empty string.

tests/lib/mirrors/unnamed_library_test.dart

Index: tests/lib/mirrors/unnamed_library_test.dart
diff --git a/tests/lib/mirrors/no_metadata_test.dart b/tests/lib/mirrors/unnamed_library_test.dart
similarity index 63%
copy from tests/lib/mirrors/no_metadata_test.dart
copy to tests/lib/mirrors/unnamed_library_test.dart
index f5c0747a59928a9d4a8c29bc82bedf659940c368..1e81eaab1284ae5b7f1d4973bfc114ce4572c471 100644
--- a/tests/lib/mirrors/no_metadata_test.dart
+++ b/tests/lib/mirrors/unnamed_library_test.dart
@@ -2,13 +2,14 @@
 // 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.
 
+// No library declaration.
+
 import 'dart:mirrors';
 
-import 'stringify.dart';
+import 'package:expect/expect.dart';
 
-class Foo {
-}
+class C {}
 
 main() {
-  expect('[]', reflectClass(Foo).metadata);
+  Expect.equals(const Symbol(""), reflectClass(C).owner.simpleName);
 }