Make Quic client more memory efficient. Protected by --quic_headers_stream_release_sequencer_buffer.

net/quic/core/quic_headers_stream.h

Index: net/quic/core/quic_headers_stream.h
diff --git a/net/quic/core/quic_headers_stream.h b/net/quic/core/quic_headers_stream.h
index 4963f6241b72e039a04e7cbb26bae5a2d924c065..b425fed0c47959c05adf326b9bfc26ecebfc64a9 100644
--- a/net/quic/core/quic_headers_stream.h
+++ b/net/quic/core/quic_headers_stream.h
@@ -95,6 +95,9 @@ class NET_EXPORT_PRIVATE QuicHeadersStream : public ReliableQuicStream {
   // server side.
   void UpdateEnableServerPush(bool value);
 
+  // Release underlying buffer if allowed.
+  void MaybeReleaseSequencerBuffer();
+
   // Sets how much encoded data the hpack decoder of spdy_framer_ is willing to
   // buffer.
   void set_max_decode_buffer_size_bytes(size_t max_decode_buffer_size_bytes) {