Add mirrors tests

test/codegen/lib/mirrors/library_imports_prefixed_show_hide.dart

Index: test/codegen/lib/mirrors/library_imports_prefixed_show_hide.dart
diff --git a/test/codegen/language/cha_deopt2_deferred_lib.dart b/test/codegen/lib/mirrors/library_imports_prefixed_show_hide.dart
similarity index 52%
copy from test/codegen/language/cha_deopt2_deferred_lib.dart
copy to test/codegen/lib/mirrors/library_imports_prefixed_show_hide.dart
index b1ef4442d30a90ca6bc8ef85cb39efe83d0a949d..ea7c71fa93ff937f2339f37ec33bb382a22e4af2 100644
--- a/test/codegen/language/cha_deopt2_deferred_lib.dart
+++ b/test/codegen/lib/mirrors/library_imports_prefixed_show_hide.dart
@@ -2,8 +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.
 
-import "cha_deopt2_lib.dart";
+library library_imports_prefixed_show_hide;
 
-class U extends T { }
+import 'library_imports_a.dart' as prefixa show somethingFromA;
+import 'library_imports_b.dart' as prefixb hide somethingFromB;
 
-make_u() => new U();
+var somethingFromPrefixed;