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

tests/lib/mirrors/library_exports_hidden.dart

Index: tests/lib/mirrors/library_exports_hidden.dart
diff --git a/tests/language/duplicate_import_prefix_test.dart b/tests/lib/mirrors/library_exports_hidden.dart
similarity index 54%
copy from tests/language/duplicate_import_prefix_test.dart
copy to tests/lib/mirrors/library_exports_hidden.dart
index 9c288029ab40a7aee66ffeb1f67467e34bdc80fc..c1ea0813f741f8cbe5c9f6de1ccf5fbcc19d30bf 100644
--- a/tests/language/duplicate_import_prefix_test.dart
+++ b/tests/lib/mirrors/library_exports_hidden.dart
@@ -2,9 +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.
 
-// Importing with a duplicate prefix is allowed.
+library library_exports_hidden;
 
-import "duplicate_import_liba.dart" as a;
-import "duplicate_import_libb.dart" as a;
+export 'library_imports_a.dart' hide somethingFromA, somethingFromBoth;
+export 'library_imports_b.dart' hide somethingFromB;
 
-void main() {}
+var somethingFromHidden;