Expose ProofSource::Details on QuicCryptoServerStream

Move ProofSource::Details caching from GfeQuicCryptoServerStream to parent class, not flag protected

PiperOrigin-RevId: 325537643
Change-Id: Idc71b12e1b7a2945e170c972e12a45707ec82457
diff --git a/quic/core/tls_server_handshaker.cc b/quic/core/tls_server_handshaker.cc
index ac3b056..bae9f1a 100644
--- a/quic/core/tls_server_handshaker.cc
+++ b/quic/core/tls_server_handshaker.cc
@@ -166,6 +166,10 @@
   return false;
 }
 
+const ProofSource::Details* TlsServerHandshaker::ProofSourceDetails() const {
+  return proof_source_details_.get();
+}
+
 void TlsServerHandshaker::OnConnectionClosed(QuicErrorCode /*error*/,
                                              ConnectionCloseSource /*source*/) {
   state_ = STATE_CONNECTION_CLOSED;