Add QUIC_EXPORT_PRIVATE to prepare for presubmit

A subsequent CL (cl/276207410) will add a presubmit to mitigate QUICHE merge issues, this CL gets our code-base to a state of compliance with that presubmit. These haven't caused issues in Chromium if they were only used in the same build unit, but it's worth it to have a consistent use across the codebase to make sure everything works in Chromium.

gfe-relnote: no behavior change, QUIC_EXPORT_PRIVATE is a no-op in google3
PiperOrigin-RevId: 276276729
Change-Id: I67ab8c9df92d24d0006de7084ca563153f0bf07f
diff --git a/quic/quic_transport/quic_transport_client_session.h b/quic/quic_transport/quic_transport_client_session.h
index 8c90aae..a39f112 100644
--- a/quic/quic_transport/quic_transport_client_session.h
+++ b/quic/quic_transport/quic_transport_client_session.h
@@ -26,7 +26,7 @@
 namespace quic {
 
 // A client session for the QuicTransport protocol.
-class QUIC_EXPORT QuicTransportClientSession
+class QUIC_EXPORT_PRIVATE QuicTransportClientSession
     : public QuicSession,
       public QuicTransportSessionInterface {
  public:
@@ -65,7 +65,7 @@
   void OnCryptoHandshakeEvent(CryptoHandshakeEvent event) override;
 
  protected:
-  class ClientIndication : public QuicStream {
+  class QUIC_EXPORT_PRIVATE ClientIndication : public QuicStream {
    public:
     using QuicStream::QuicStream;