Update dart:async to match the Dart repo.

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 f54d92a40e2f26f4131d3059bfa536f9fd0e030e..f373361190aa888e6f2e6a108a066008da1cd7db 100644
--- a/tool/sdk_expected_errors.txt
+++ b/tool/sdk_expected_errors.txt
@@ -1,8 +1,8 @@
 [error] The argument type 'InternalMap' cannot be assigned to the parameter type 'Map'. (dart:_isolate_helper/isolate_serialization.dart, line 47, col 47)
 [error] Missing concrete implementation of 'num.==' (dart:_interceptors/js_number.dart, line 12, col 7)
 [error] Missing concrete implementation of 'String.==' (dart:_interceptors/js_string.dart, line 14, col 7)
-[error] Type check failed: (_BroadcastSubscription<T> subscription) {subscription._close();} ((_BroadcastSubscription<T>) → void) is not of type (_BufferingStreamSubscription<T>) → void (dart:async/broadcast_stream_controller.dart, line 371, col 24)
 [error] Annotation can be only constant variable or constant constructor invocation (dart:core/stacktrace.dart, line 27, col 3)
+[error] Invalid override. The type of _EventStreamSubscription.asFuture (([dynamic]) → Future<dynamic>) is not a subtype of StreamSubscription<T>.asFuture (<E>([E]) → Future<E>). (dart:html, line 40153, col 3)
 [error] The part was not supplied as an input to the compiler. (dart:html_common/conversions.dart, line 1, col 1)
 [error] The part was not supplied as an input to the compiler. (dart:html_common/conversions_dart2js.dart, line 1, col 1)
 [error] The part was not supplied as an input to the compiler. (dart:html_common/css_class_set.dart, line 1, col 1)
@@ -33,65 +33,6 @@
 [warning] Unsound implicit cast from dynamic to List<String> (dart:_js_helper/regexp_helper.dart, line 108, col 22)
 [warning] Unsound implicit cast from List<dynamic> to List<String> (dart:_js_helper/regexp_helper.dart, line 140, col 43)
 [warning] Unsound implicit cast from List<dynamic> to List<String> (dart:_js_helper/regexp_helper.dart, line 152, col 43)
-[warning] Unsound implicit cast from _StreamControllerLifecycle<dynamic> to _StreamControllerLifecycle<T> (dart:async/broadcast_stream_controller.dart, line 8, col 67)
-[warning] Unsound implicit cast from _StreamControllerLifecycle<dynamic> to _StreamControllerLifecycle<T> (dart:async/broadcast_stream_controller.dart, line 36, col 15)
-[warning] Unsound implicit cast from StreamSubscription<dynamic> to _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 194, col 18)
-[warning] Unsound implicit cast from StreamSubscription<dynamic> to StreamSubscription<T> (dart:async/broadcast_stream_controller.dart, line 199, col 12)
-[warning] Unsound implicit cast from _BroadcastSubscriptionLink to _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 308, col 48)
-[warning] Unsound implicit cast from _BroadcastSubscriptionLink to _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 392, col 48)
-[warning] Unsound implicit cast from _BroadcastSubscriptionLink to _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 401, col 48)
-[warning] Unsound implicit cast from _BroadcastSubscriptionLink to _BroadcastSubscription<T> (dart:async/broadcast_stream_controller.dart, line 411, col 50)
-[warning] Unsound implicit cast from _Future<dynamic> to Future<T> (dart:async/future.dart, line 123, col 12)
-[warning] Unsound implicit cast from _Future<dynamic> to Future<T> (dart:async/future.dart, line 149, col 12)
-[warning] Unsound implicit cast from _Future<dynamic> to Future<T> (dart:async/future.dart, line 233, col 12)
-[warning] Unsound implicit cast from Object to T (dart:async/future.dart, line 297, col 25)
-[warning] Unsound implicit cast from Object to T (dart:async/future.dart, line 304, col 42)
-[warning] Unsound implicit cast from Function to (dynamic) → bool (dart:async/future_impl.dart, line 117, col 12)
-[warning] Unsound implicit cast from (dynamic) → dynamic to (T) → S (dart:async/future_impl.dart, line 208, col 11)
-[warning] Unsound implicit cast from (dynamic) → dynamic to (dynamic) → bool (dart:async/future_impl.dart, line 221, col 32)
-[warning] Unsound implicit cast from _Future<dynamic> to Future<T> (dart:async/future_impl.dart, line 233, col 12)
-[warning] Unsound implicit cast from dynamic to T (dart:async/future_impl.dart, line 245, col 12)
-[warning] Unsound implicit cast from dynamic to T (dart:async/future_impl.dart, line 347, col 17)
-[warning] Unsound implicit cast from dynamic to T (dart:async/future_impl.dart, line 357, col 15)
-[warning] Unsound implicit cast from Future<dynamic> to Future<T> (dart:async/future_impl.dart, line 386, col 31)
-[warning] Unsound implicit cast from dynamic to T (dart:async/future_impl.dart, line 407, col 22)
-[warning] Unsound implicit cast from dynamic to () → void (dart:async/schedule_microtask.dart, line 66, col 61)
-[warning] Unsound implicit cast from dynamic to () → void (dart:async/schedule_microtask.dart, line 71, col 60)
-[warning] Unsound implicit cast from dynamic to () → void (dart:async/schedule_microtask.dart, line 84, col 55)
-[warning] Unsound implicit cast from (StreamSubscription<T>) → void to (StreamSubscription<dynamic>) → void (dart:async/stream.dart, line 249, col 44)
-[warning] Unsound implicit cast from (StreamSubscription<T>) → void to (StreamSubscription<dynamic>) → void (dart:async/stream.dart, line 249, col 54)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 503, col 24)
-[warning] Unsound implicit cast from dynamic to S (dart:async/stream.dart, line 536, col 32)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 537, col 11)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 605, col 13)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 631, col 13)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 660, col 13)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 697, col 13)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 1039, col 11)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 1080, col 11)
-[warning] Unsound implicit cast from dynamic to (dynamic, StackTrace) → dynamic (dart:async/stream.dart, line 1132, col 11)
-[warning] Unsound implicit cast from Function to () → void (dart:async/stream.dart, line 1222, col 43)
-[warning] Unsound implicit cast from Function to () → void (dart:async/stream.dart, line 1230, col 43)
-[warning] Unsound implicit cast from (dynamic) → dynamic to (EventSink<dynamic>) → void (dart:async/stream.dart, line 1248, col 21)
-[warning] Unsound implicit cast from Function to () → void (dart:async/stream.dart, line 1259, col 43)
-[warning] Unsound implicit cast from Function to () → void (dart:async/stream.dart, line 1278, col 53)
-[warning] Unsound implicit cast from _ControllerSubscription<dynamic> to StreamSubscription<T> (dart:async/stream_controller.dart, line 516, col 12)
-[warning] Unsound implicit cast from _StreamController<dynamic> to _EventSink<T> (dart:async/stream_controller.dart, line 798, col 15)
-[warning] Unsound implicit cast from (dynamic) → dynamic to (T) → void (dart:async/stream_impl.dart, line 154, col 15)
-[warning] Unsound implicit cast from StreamSubscription<dynamic> to StreamSubscription<T> (dart:async/stream_impl.dart, line 476, col 12)
-[warning] Unsound implicit cast from (dynamic) → dynamic to (StreamSubscription<dynamic>) → void (dart:async/stream_impl.dart, line 813, col 28)
-[warning] Unsound implicit cast from (dynamic) → dynamic to (StreamSubscription<dynamic>) → void (dart:async/stream_impl.dart, line 814, col 28)
-[warning] Unsound implicit cast from dynamic to Future<bool> (dart:async/stream_impl.dart, line 1000, col 14)
-[warning] Unsound implicit cast from dynamic to T (dart:async/stream_impl.dart, line 1006, col 22)
-[warning] Unsound implicit cast from dynamic to _Future<bool> (dart:async/stream_impl.dart, line 1035, col 31)
-[warning] Unsound implicit cast from dynamic to _Future<bool> (dart:async/stream_impl.dart, line 1047, col 31)
-[warning] Unsound implicit cast from dynamic to _Future<bool> (dart:async/stream_impl.dart, line 1061, col 31)
-[warning] Unsound implicit cast from dynamic to _Future<bool> (dart:async/stream_impl.dart, line 1075, col 31)
-[warning] Unsound implicit cast from dynamic to T (dart:async/stream_pipe.dart, line 104, col 15)
-[warning] Unsound implicit cast from dynamic to T (dart:async/stream_pipe.dart, line 235, col 21)
-[warning] Unsound implicit cast from Object to T (dart:async/stream_pipe.dart, line 426, col 29)
-[warning] Unsound implicit cast from (dynamic) → dynamic to (Timer) → void (dart:async/timer.dart, line 80, col 19)
-[warning] Unsound implicit cast from (dynamic) → dynamic to (Timer) → void (dart:async/zone.dart, line 962, col 16)
 [warning] Unsound implicit cast from dynamic to V (dart:collection, line 98, col 14)
 [warning] Unsound implicit cast from dynamic to V (dart:collection, line 101, col 14)
 [warning] Unsound implicit cast from dynamic to V (dart:collection, line 112, col 12)