Initialize _BroadcastSubscription._eventState to permit inference of non-null value

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;
 }
 
 abstract class _BroadcastSubscriptionLink {
   _BroadcastSubscriptionLink _next;
   _BroadcastSubscriptionLink _previous;
 }
 
 class _BroadcastSubscription<T> extends _ControllerSubscription<T>
                                 implements _BroadcastSubscriptionLink {
   static const int _STATE_EVENT_ID = 1;
   static const int _STATE_FIRING = 2;
   static const int _STATE_REMOVE_AFTER_FIRING = 4;
   // TODO(lrn): Use the _state field on _ControllerSubscription to
   // also store this state. Requires that the subscription implementation
   // does not assume that it's use of the state integer is the only use.
-  int _eventState;
+  int _eventState = 0;  // Initialized to help dart2js type inference.
 
   _BroadcastSubscriptionLink _next;
   _BroadcastSubscriptionLink _previous;
 
   _BroadcastSubscription(_StreamControllerLifecycle controller,
                          void onData(T data),
                          Function onError,
                          void onDone(),
                          bool cancelOnError)
       : super(controller, onData, onError, onDone, cancelOnError) {
@@ skipping 496 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();
 }