Do not crash on null stream in writing to bidirectional streams

net/spdy/bidirectional_stream_spdy_impl.h

Index: net/spdy/bidirectional_stream_spdy_impl.h
diff --git a/net/spdy/bidirectional_stream_spdy_impl.h b/net/spdy/bidirectional_stream_spdy_impl.h
index 06d0d351f1be3d8b7672de34ed3dd956696aa0fc..629c7a331e8ed8911a962a100e1cf820c412fcd8 100644
--- a/net/spdy/bidirectional_stream_spdy_impl.h
+++ b/net/spdy/bidirectional_stream_spdy_impl.h
@@ -70,6 +70,8 @@ class NET_EXPORT_PRIVATE BidirectionalStreamSpdyImpl
  private:
   int SendRequestHeadersHelper();
   void OnStreamInitialized(int rv);
+  // Notifies delegate of an error.
+  void NotifyError(int rv);
   void ScheduleBufferedRead();
   void DoBufferedRead();
   bool ShouldWaitForMoreBufferedData() const;