gfe-relnote: Fix invalid downcast.

QuicTransportServerSessionTest fails on UBSAN builds in Chromium, see
https://crrev.com/c/2015242.

QuicTransportServerSession initializes |crypto_stream_| in the constructor using
CreateCryptoServerStream(), which since cr/290819354 might return a
TlsServerHandshaker, which is a derived class of QuicCryptoServerStreamBase but
not of QuicCryptoServerStream.  Hence the downcast fails in
QuicTransportServerSessionTest constructor.  Fortunately
QuicTransportServerSessionTest does not need a QuicCryptoServerStream, only a
QuicCryptoServerStreamBase: it calls OnSuccessfulVersionNegotiation() which is a
QuicCryptoStream method, and passes it to  HandshakeWithFakeClient() which takes
a QuicCryptoServerStreamBase*.
PiperOrigin-RevId: 291203032
Change-Id: I7b3ec41c64eeb46074ee6aa98bff7bd132a20daa

quic/quic_transport/quic_transport_server_session.h

diff --git a/quic/quic_transport/quic_transport_server_session.h b/quic/quic_transport/quic_transport_server_session.h
index c023264..e756360 100644
--- a/quic/quic_transport/quic_transport_server_session.h
+++ b/quic/quic_transport/quic_transport_server_session.h
@@ -51,10 +51,10 @@
 
   bool ShouldKeepConnectionAlive() const override { return true; }
 
-  QuicCryptoStream* GetMutableCryptoStream() override {
+  QuicCryptoServerStreamBase* GetMutableCryptoStream() override {
     return crypto_stream_.get();
   }
-  const QuicCryptoStream* GetCryptoStream() const override {
+  const QuicCryptoServerStreamBase* GetCryptoStream() const override {
     return crypto_stream_.get();
   }
 

quic/quic_transport/quic_transport_server_session_test.cc

diff --git a/quic/quic_transport/quic_transport_server_session_test.cc b/quic/quic_transport/quic_transport_server_session_test.cc
index f74fb53..2f0a0e8 100644
--- a/quic/quic_transport/quic_transport_server_session_test.cc
+++ b/quic/quic_transport/quic_transport_server_session_test.cc
@@ -74,8 +74,7 @@
         &connection_, nullptr, DefaultQuicConfig(), GetVersions(),
         &crypto_config_, &compressed_certs_cache_, &visitor_);
     session_->Initialize();
-    crypto_stream_ = static_cast<QuicCryptoServerStream*>(
-        session_->GetMutableCryptoStream());
+    crypto_stream_ = session_->GetMutableCryptoStream();
     if (!GetQuicReloadableFlag(quic_version_negotiated_by_default_at_server)) {
       crypto_stream_->OnSuccessfulVersionNegotiation(GetVersions()[0]);
     }
@@ -130,7 +129,7 @@
   std::unique_ptr<QuicTransportServerSession> session_;
   QuicCompressedCertsCache compressed_certs_cache_;
   testing::NiceMock<MockServerVisitor> visitor_;
-  QuicCryptoServerStream* crypto_stream_;
+  QuicCryptoServerStreamBase* crypto_stream_;
   GURL path_;
 };