lazy allocation and early release memory in QuicStreamSequencerBuffer. Protected by --quic_reduce_s…

net/quic/core/quic_stream_sequencer.h

Index: net/quic/core/quic_stream_sequencer.h
diff --git a/net/quic/core/quic_stream_sequencer.h b/net/quic/core/quic_stream_sequencer.h
index 16a6ecaafff7801b3432d917f035d414c985b1b3..032616ccba16ecec17974ad0e5ecabf2fd15ea93 100644
--- a/net/quic/core/quic_stream_sequencer.h
+++ b/net/quic/core/quic_stream_sequencer.h
@@ -79,6 +79,9 @@ class NET_EXPORT_PRIVATE QuicStreamSequencer {
   // automatically when the FIN is consumed (which may be immediately).
   void StopReading();
 
+  // Free the memory of underlying buffer.
+  void ReleaseBuffer();
+
   // Number of bytes in the buffer right now.
   size_t NumBytesBuffered() const;