Exposes an accessor within QuicStream for the number of bytes consumed on a stream.

Protected by unused new code, not protected.

PiperOrigin-RevId: 628256910
diff --git a/quiche/quic/core/quic_stream.h b/quiche/quic/core/quic_stream.h
index 4ce0d3a..9260045 100644
--- a/quiche/quic/core/quic_stream.h
+++ b/quiche/quic/core/quic_stream.h
@@ -262,6 +262,9 @@
   bool IsFlowControlBlocked() const;
   QuicStreamOffset highest_received_byte_offset() const;
   void UpdateReceiveWindowSize(QuicStreamOffset size);
+  QuicStreamOffset NumBytesConsumed() const {
+    return sequencer()->NumBytesConsumed();
+  }
 
   // Called when endpoint receives a frame which could increase the highest
   // offset.