Use NumBytesConsumed() to determine number of bytes associated with request.

Use NumBytesConsumed() instead of stream_bytes_read(), as the latter
double-counts retransmitted bytes.

Protected by FLAGS_gfe2_reloadable_flag_fix_h3_request_size2.

PiperOrigin-RevId: 599899093

quiche/quic/core/qpack/qpack_receive_stream.h

diff --git a/quiche/quic/core/qpack/qpack_receive_stream.h b/quiche/quic/core/qpack/qpack_receive_stream.h
index 173d28c..07e7594 100644
--- a/quiche/quic/core/qpack/qpack_receive_stream.h
+++ b/quiche/quic/core/qpack/qpack_receive_stream.h
@@ -32,6 +32,11 @@
   // Implementation of QuicStream.
   void OnDataAvailable() override;
 
+  // Number of incoming bytes that have been consumed on this stream.
+  QuicStreamOffset NumBytesConsumed() const {
+    return sequencer()->NumBytesConsumed();
+  }
+
  private:
   QpackStreamReceiver* receiver_;
 };