Add mirrors tests

test/codegen/lib/mirrors/library_imports_a.dart

Index: test/codegen/lib/mirrors/library_imports_a.dart
diff --git a/test/codegen/language/cha_deopt1_lib.dart b/test/codegen/lib/mirrors/library_imports_a.dart
similarity index 75%
copy from test/codegen/language/cha_deopt1_lib.dart
copy to test/codegen/lib/mirrors/library_imports_a.dart
index f49562de496f7f432b7fb2d41dfd5fb60df9091b..afdc329c609bd174f349ff5df20ebc3783851ec6 100644
--- a/test/codegen/language/cha_deopt1_lib.dart
+++ b/test/codegen/lib/mirrors/library_imports_a.dart
@@ -2,11 +2,7 @@
 // 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.
 
-library mylib;
-
-class T {
-
-  m() => 42;
-
-}
+library library_imports_a;
 
+var somethingFromA;
+var somethingFromBoth;