Fix field override error

tool/input_sdk/lib/async/broadcast_stream_controller.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.async;
 
 class _BroadcastStream<T> extends _ControllerStream<T> {
   _BroadcastStream(_StreamControllerLifecycle controller) : super(controller);
 
   bool get isBroadcast => true;
@@ skipping 19 matching lines @@
 
   _BroadcastSubscription(_StreamControllerLifecycle controller,
                          void onData(T data),
                          Function onError,
                          void onDone(),
                          bool cancelOnError)
       : super(controller, onData, onError, onDone, cancelOnError) {
     _next = _previous = this;
   }
 
-  _BroadcastStreamController<T> get _controller => super._controller;
-
   bool _expectsEvent(int eventId) =>
       (_eventState & _STATE_EVENT_ID) == eventId;
 
   void _toggleEventId() {
     _eventState ^= _STATE_EVENT_ID;
   }
 
   bool get _isFiring => (_eventState & _STATE_FIRING) != 0;
 
   void _setRemoveAfterFiring() {
@@ skipping 452 matching lines @@
     _pauseCount++;
   }
   void resume() { _resume(null); }
   void _resume(_) {
     if (_pauseCount > 0) _pauseCount--;
   }
   Future cancel() { return new _Future.immediate(null); }
   bool get isPaused => _pauseCount > 0;
   Future asFuture([Object value]) => new _Future();
 }