Add APIs to allow sessions to read stream types from pending stream.

Pending stream will now allow receiving stream frame with zero offset.

gfe-relnote: version 99 only. Only used in test.
PiperOrigin-RevId: 247277571
Change-Id: Ib7986a27ce0106efd3102b50bfe82f0eac4b9fe3
diff --git a/quic/core/quic_stream.h b/quic/core/quic_stream.h
index 0cacbe3..efe46a6 100644
--- a/quic/core/quic_stream.h
+++ b/quic/core/quic_stream.h
@@ -73,6 +73,8 @@
   // Returns the number of bytes read on this stream.
   uint64_t stream_bytes_read() { return stream_bytes_read_; }
 
+  const QuicStreamSequencer* sequencer() const { return &sequencer_; }
+
  private:
   friend class QuicStream;