Migrate block 163 to Dart 2.0.

tests/language_2/unused_overridden_async_test.dart

Index: tests/language_2/unused_overridden_async_test.dart
diff --git a/tests/language_strong/unused_overridden_async_test.dart b/tests/language_2/unused_overridden_async_test.dart
similarity index 96%
rename from tests/language_strong/unused_overridden_async_test.dart
rename to tests/language_2/unused_overridden_async_test.dart
index 37286bbcef214875a1040dcb1da0ea0402017c58..da7aa72b9cb1c54c7dd9430e57e630602bd6422a 100644
--- a/tests/language_strong/unused_overridden_async_test.dart
+++ b/tests/language_2/unused_overridden_async_test.dart
@@ -10,14 +10,12 @@ class Base {
 }
 
 class Sub1 extends Base {
-  @override
   Future<int> method() async {
     return 1;
   }
 }
 
 class Sub2 extends Base {
-  @override
   Future<int> method() async {
     return 2;
   }