Make new StreamController be async by default.

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 375844cdcdf535ce2d3a502714e3fc4363e56a59..e46ba50aedd64a76028251fa5b492692d9ce7c0b 100644
--- a/sdk/lib/async/stream_impl.dart
+++ b/sdk/lib/async/stream_impl.dart
@@ -694,9 +694,9 @@ class _StreamImplEvents extends _PendingEvents {
   }
 }
 
-class _MultiplexerLinkedList {
-  _MultiplexerLinkedList _next;
-  _MultiplexerLinkedList _previous;
+class _BroadcastLinkedList {
+  _BroadcastLinkedList _next;
+  _BroadcastLinkedList _previous;
 
   void _unlink() {
     _previous._next = _next;
@@ -704,8 +704,8 @@ class _MultiplexerLinkedList {
     _next = _previous = this;
   }
 
-  void _insertBefore(_MultiplexerLinkedList newNext) {
-    _MultiplexerLinkedList newPrevious = newNext._previous;
+  void _insertBefore(_BroadcastLinkedList newNext) {
+    _BroadcastLinkedList newPrevious = newNext._previous;
     newPrevious._next = this;
     newNext._previous = _previous;
     _previous._next = newNext;
@@ -715,11 +715,11 @@ class _MultiplexerLinkedList {
 
 class _AsBroadcastStream<T> extends Stream<T> {
   final Stream<T> _source;
-  _BufferingMultiplexStreamController<T> _controller;
+  _AsBroadcastStreamController<T> _controller;
   StreamSubscription<T> _subscription;
 
   _AsBroadcastStream(this._source) {
-    _controller = new _BufferingMultiplexStreamController<T>(null, _onCancel);
+    _controller = new _AsBroadcastStreamController<T>(null, _onCancel);
   }
 
   bool get isBroadcast => true;