Fix owner of mixin forwarding constructors

tests/language/regress_25246_2.dart

Index: tests/language/regress_25246_2.dart
diff --git a/tests/language/deferred_super_dependency_lib.dart b/tests/language/regress_25246_2.dart
similarity index 66%
copy from tests/language/deferred_super_dependency_lib.dart
copy to tests/language/regress_25246_2.dart
index a592dabbae9fbb321b2f5c088e1267997af0e6fa..84c9cfb4f4573da8ad399619b0e1d0234d43bd48 100644
--- a/tests/language/deferred_super_dependency_lib.dart
+++ b/tests/language/regress_25246_2.dart
@@ -2,11 +2,11 @@
 // 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.
 
-class A {
-}
+import 'regress_25246_3.dart';
 
-class C extends A {
-  foo() {
-    super.foo = 3;
+class MixIn {
+  var test3 = new Test3(() { });
+  void test() {
+    test3.test();
   }
-}
+}