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

net/quic/core/quic_client_session_base.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_QUIC_QUIC_CLIENT_SESSION_BASE_H_
 #define NET_QUIC_QUIC_CLIENT_SESSION_BASE_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 93 matching lines @@
   virtual void DeletePromised(QuicClientPromisedInfo* promised);
 
   virtual void OnPushStreamTimedOut(QuicStreamId stream_id);
 
   // Sends Rst for the stream, and makes sure that future calls to
   // IsClosedStream(id) return true, which ensures that any subsequent
   // frames related to this stream will be ignored (modulo flow
   // control accounting).
   void ResetPromised(QuicStreamId id, QuicRstStreamErrorCode error_code);
 
+  // Release headers stream's sequencer buffer if it's empty.
+  void CloseStreamInner(QuicStreamId stream_id, bool locally_reset) override;
+
+  // Returns true if there are no active requests and no promised streams.
+  bool ShouldReleaseHeadersStreamSequencerBuffer() override;
+
   size_t get_max_promises() const {
     return max_open_incoming_streams() * kMaxPromisedStreamsMultiplier;
   }
 
   QuicClientPushPromiseIndex* push_promise_index() {
     return push_promise_index_;
   }
 
  private:
   // For QuicSpdyClientStream to detect that a response corresponds to a
   // promise.
   using QuicPromisedByIdMap =
       std::unordered_map<QuicStreamId, std::unique_ptr<QuicClientPromisedInfo>>;
 
   // As per rfc7540, section 10.5: track promise streams in "reserved
   // (remote)".  The primary key is URL from he promise request
   // headers.  The promised stream id is a secondary key used to get
   // promise info when the response headers of the promised stream
   // arrive.
   QuicClientPushPromiseIndex* push_promise_index_;
   QuicPromisedByIdMap promised_by_id_;
   QuicStreamId largest_promised_stream_id_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicClientSessionBase);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_CLIENT_SESSION_BASE_H_