Fix field override error

tool/sdk_expected_errors.txt

Index: tool/sdk_expected_errors.txt
diff --git a/tool/sdk_expected_errors.txt b/tool/sdk_expected_errors.txt
index b63b40f6a28ef1fc776a875b210ac4116a8ecaf8..864b49a2e46881b3d990de6239080b88704397a6 100644
--- a/tool/sdk_expected_errors.txt
+++ b/tool/sdk_expected_errors.txt
@@ -25,13 +25,13 @@ warning: [DownCastComposite] match (List<dynamic>) will need runtime check to ca
 warning: [DownCastComposite] pattern.allMatches(receiver) (dynamic) will need runtime check to cast to type Iterable<Match> (dart:_js_helper/string_helper.dart, line 137, col 23)
 warning: [DownCastComposite] controller (_StreamControllerLifecycle<dynamic>) will need runtime check to cast to type _StreamControllerLifecycle<T> (dart:async/broadcast_stream_controller.dart, line 8, col 67)
 warning: [DownCastComposite] controller (_StreamControllerLifecycle<dynamic>) will need runtime check to cast to type _StreamControllerLifecycle<T> (dart:async/broadcast_stream_controller.dart, line 36, col 15)
-warning: [DownCastComposite] subscription (StreamSubscription<dynamic>) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 196, col 18)
-warning: [DownCastComposite] subscription (StreamSubscription<dynamic>) will need runtime check to cast to type StreamSubscription<T> (dart:async/broadcast_stream_controller.dart, line 201, col 12)
-warning: [DownCastComposite] link (_BroadcastSubscriptionLink) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 310, col 48)
-warning: [UninferredClosure] (_BroadcastSubscription<T> subscription) {subscription._close();} ((_BroadcastSubscription<T>) → dynamic) will need runtime check to cast to type (_BufferingStreamSubscription<T>) → void (dart:async/broadcast_stream_controller.dart, line 373, col 24)
-warning: [DownCastComposite] link (_BroadcastSubscriptionLink) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 394, col 48)
-warning: [DownCastComposite] link (_BroadcastSubscriptionLink) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 403, col 48)
-warning: [DownCastComposite] link (_BroadcastSubscriptionLink) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 413, col 50)
+warning: [DownCastComposite] subscription (StreamSubscription<dynamic>) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 194, col 18)
+warning: [DownCastComposite] subscription (StreamSubscription<dynamic>) will need runtime check to cast to type StreamSubscription<T> (dart:async/broadcast_stream_controller.dart, line 199, col 12)
+warning: [DownCastComposite] link (_BroadcastSubscriptionLink) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 308, col 48)
+warning: [UninferredClosure] (_BroadcastSubscription<T> subscription) {subscription._close();} ((_BroadcastSubscription<T>) → dynamic) will need runtime check to cast to type (_BufferingStreamSubscription<T>) → void (dart:async/broadcast_stream_controller.dart, line 371, col 24)
+warning: [DownCastComposite] link (_BroadcastSubscriptionLink) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 392, col 48)
+warning: [DownCastComposite] link (_BroadcastSubscriptionLink) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 401, col 48)
+warning: [DownCastComposite] link (_BroadcastSubscriptionLink) will need runtime check to cast to type _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 411, col 50)
 warning: [DownCastComposite] result (_Future<dynamic>) will need runtime check to cast to type Future<T> (dart:async/future.dart, line 123, col 12)
 warning: [DownCastComposite] result (_Future<dynamic>) will need runtime check to cast to type Future<T> (dart:async/future.dart, line 149, col 12)
 warning: [DownCastComposite] result (_Future<dynamic>) will need runtime check to cast to type Future<T> (dart:async/future.dart, line 233, col 12)