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

net/quic/core/quic_spdy_session.h

Index: net/quic/core/quic_spdy_session.h
diff --git a/net/quic/core/quic_spdy_session.h b/net/quic/core/quic_spdy_session.h
index b4db9288efc1ceb1d3348b53abf6782618332b15..37f40494659985d5be701123ef5f2d5acf53289c 100644
--- a/net/quic/core/quic_spdy_session.h
+++ b/net/quic/core/quic_spdy_session.h
@@ -116,6 +116,10 @@ class NET_EXPORT_PRIVATE QuicSpdySession : public QuicSession {
   // value from SETTINGS_ENABLE_PUSH.
   void set_server_push_enabled(bool enable) { server_push_enabled_ = enable; }
 
+  // Return true if this session wants to release headers stream's buffer
+  // aggressively.
+  virtual bool ShouldReleaseHeadersStreamSequencerBuffer();
+
  protected:
   // Override CreateIncomingDynamicStream() and CreateOutgoingDynamicStream()
   // with QuicSpdyStream return type to make sure that all data streams are