Add DV2 logs to help interop debugging

gfe-relnote: adds QUIC_DVLOG(2) logs that are not enabled in production, not flag-protected
PiperOrigin-RevId: 253144347
Change-Id: Ia632d5622aee919b9aa2a84b5bf729c8bde916d1
diff --git a/quic/core/frames/quic_frame.h b/quic/core/frames/quic_frame.h
index caa5fce..1fa9e01 100644
--- a/quic/core/frames/quic_frame.h
+++ b/quic/core/frames/quic_frame.h
@@ -140,6 +140,9 @@
 QUIC_EXPORT_PRIVATE QuicFrame
 CopyRetransmittableControlFrame(const QuicFrame& frame);
 
+// Human-readable description suitable for logging.
+QUIC_EXPORT_PRIVATE std::string QuicFramesToString(const QuicFrames& frames);
+
 }  // namespace quic
 
 #endif  // QUICHE_QUIC_CORE_FRAMES_QUIC_FRAME_H_