Make QuicSession::OnStreamClosed() more robust.

Since we don't have the stream close loop anymore, closing stream twice is not expected.

No behavior change. not protected.

PiperOrigin-RevId: 320273993
Change-Id: I90c9162b41ef972eea5731eb74fe524d8f25fd5e
diff --git a/quic/core/http/quic_spdy_session_test.cc b/quic/core/http/quic_spdy_session_test.cc
index fea8541..df83890 100644
--- a/quic/core/http/quic_spdy_session_test.cc
+++ b/quic/core/http/quic_spdy_session_test.cc
@@ -161,6 +161,9 @@
 
   MOCK_METHOD(bool, HasPendingRetransmission, (), (const, override));
 
+  void OnConnectionClosed(QuicErrorCode /*error*/,
+                          ConnectionCloseSource /*source*/) override {}
+
  private:
   using QuicCryptoStream::session;