Reapply "Access to imports in the VM's runtime mirrors. Extend test coverage of the source mirrors."

tests/compiler/dart2js/mirrors/library_imports_prefixed_test.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// Copyright (c) 2014, 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.
 
 import "dart:mirrors";
 
 import "package:async_helper/async_helper.dart";
 
 import "mirrors_test_helper.dart";
-import "../../../lib/mirrors/relation_subclass_test.dart";
+import "../../../lib/mirrors/library_imports_prefixed_test.dart";
 
 main() {
-  asyncTest(() => analyze("relation_subclass_test.dart").
+  asyncTest(() => analyze("library_imports_prefixed_test.dart").
       then((MirrorSystem mirrors) {
     test(mirrors);
   }));
 }