fixes #27385, implement virtual fields in DDC

tests/language_strong/super_field_2_test.dart

Index: tests/language_strong/super_field_2_test.dart
diff --git a/tests/language_strong/super_field_2_test.dart b/tests/language_strong/super_field_2_test.dart
index 7c53c43cba2c3e8a568757e0ce0616123cf57df4..304e4ef0ac66155bcfa70ec6c26a730159b6ec5c 100644
--- a/tests/language_strong/super_field_2_test.dart
+++ b/tests/language_strong/super_field_2_test.dart
@@ -3,9 +3,10 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import "package:expect/expect.dart";
+import "package:meta/meta.dart" show virtual;
 
 class A {
-  var foo;
+  @virtual var foo;
   A(this.foo);
 
   B_Sfoo() => 'A.B_Sfoo()';