fixes #27385, implement virtual fields in DDC

tests/language_strong/getter_override2_test.dart

Index: tests/language_strong/getter_override2_test.dart
diff --git a/tests/language_strong/getter_override2_test.dart b/tests/language_strong/getter_override2_test.dart
index ec162de28e97780c71d58828276c2bdd686adc62..0fc4c5aff58a9405b427a98b7447a6356bdcc6e6 100644
--- a/tests/language_strong/getter_override2_test.dart
+++ b/tests/language_strong/getter_override2_test.dart
@@ -6,9 +6,10 @@
 // with an inherited instance method of the same name.
 
 import "package:expect/expect.dart";
+import "package:meta/meta.dart" show virtual;
 
 class A {
-  var foo = 42;  /// 00: ok
+  @virtual var foo = 42;  /// 00: ok
   get foo => 42;  /// 01: ok
   foo() => 42;  /// 02: compile-time error
   set foo(value) { }  /// 03: ok