Fix bug in web socket close handling

runtime/bin/websocket_impl.dart

Index: runtime/bin/websocket_impl.dart
diff --git a/runtime/bin/websocket_impl.dart b/runtime/bin/websocket_impl.dart
index a23fde4bc96c976b2dc289dd6dcaecd8e1378ca1..b9534e37aba2484a79546094722aae4cfd7b34ff 100644
--- a/runtime/bin/websocket_impl.dart
+++ b/runtime/bin/websocket_impl.dart
@@ -445,7 +445,7 @@ class _WebSocketConnectionBase  {
       // Half close the socket and expect a close frame in response
       // before closing the socket. If a close frame does not arrive
       // within a reasonable amount of time just close the socket.
-      _socket.close(true);
+      _socket.outputStream.close();
       _closeTimer = new Timer(5000, (t) {
         _socket.close();
       });