message: Send app event that a newly created stream is writable
diff: @@ -428,6 +428,9 @@ impl SendStream {
  flow_mgr: Rc<RefCell<FlowMgr>>,
  conn_events: Rc<RefCell<ConnectionEvents>>,
  ) -> SendStream {
  + if max_stream_data > 0 {
  + conn_events.borrow_mut().send_stream_writable(stream_id);
  + }
  SendStream {
  stream_id,
  max_stream_data,
  