Log more detailed info when dumping GfeQuicClientStream.

PiperOrigin-RevId: 722703697

quiche/quic/core/http/quic_spdy_client_stream.h

diff --git a/quiche/quic/core/http/quic_spdy_client_stream.h b/quiche/quic/core/http/quic_spdy_client_stream.h
index e8537bf..66b0041 100644
--- a/quiche/quic/core/http/quic_spdy_client_stream.h
+++ b/quiche/quic/core/http/quic_spdy_client_stream.h
@@ -53,11 +53,11 @@
   absl::string_view data() const { return data_; }
 
   // Returns whatever headers have been received for this stream.
-  const quiche::HttpHeaderBlock& response_headers() {
+  const quiche::HttpHeaderBlock& response_headers() const {
     return response_headers_;
   }
 
-  const std::list<quiche::HttpHeaderBlock>& preliminary_headers() {
+  const std::list<quiche::HttpHeaderBlock>& preliminary_headers() const {
     return preliminary_headers_;
   }