additional SDK fixes. This gets all of them, once we upgrade to new analyzer

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 183 matching lines @@
         new _BroadcastSubscription<T>(this, onData, onError, onDone,
                                       cancelOnError);
     _addListener(subscription);
     if (identical(_next, _previous)) {
       // Only one listener, so it must be the first listener.
       _runGuarded(_onListen);
     }
     return subscription;
   }
 
-  Future _recordCancel(StreamSubscription<T> subscription) {
+  Future _recordCancel(StreamSubscription<T> sub) {
+    var subscription = sub as _BroadcastSubscription<T>;
     // If already removed by the stream, don't remove it again.
     if (identical(subscription._next, subscription)) return null;
     assert(!identical(subscription._next, subscription));
     if (subscription._isFiring) {
       subscription._setRemoveAfterFiring();
     } else {
       assert(!identical(subscription._next, subscription));
       _removeListener(subscription);
       // If we are currently firing an event, the empty-check is performed at
       // the end of the listener loop instead of here.
@@ skipping 288 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();
 }