Add type to BroadcastSubscriptionWrapper.

sdk/lib/async/stream_impl.dart

Index: sdk/lib/async/stream_impl.dart
diff --git a/sdk/lib/async/stream_impl.dart b/sdk/lib/async/stream_impl.dart
index c23b0f040f6924d75f1b922f150e1d3765b28d3c..c5481a3da442422f795f34da110c58dce77ba8c0 100644
--- a/sdk/lib/async/stream_impl.dart
+++ b/sdk/lib/async/stream_impl.dart
@@ -839,7 +839,8 @@ class _AsBroadcastStream<T> extends Stream<T> {
   void _onCancel() {
     bool shutdown = (_controller == null) || _controller.isClosed;
     if (_onCancelHandler != null) {
-      _zone.runUnary(_onCancelHandler, new _BroadcastSubscriptionWrapper(this));
+      _zone.runUnary(
+          _onCancelHandler, new _BroadcastSubscriptionWrapper<T>(this));
     }
     if (shutdown) {
       if (_subscription != null) {
@@ -851,7 +852,8 @@ class _AsBroadcastStream<T> extends Stream<T> {
 
   void _onListen() {
     if (_onListenHandler != null) {
-      _zone.runUnary(_onListenHandler, new _BroadcastSubscriptionWrapper(this));
+      _zone.runUnary(
+          _onListenHandler, new _BroadcastSubscriptionWrapper<T>(this));
     }
   }