Send QUIC ping packets when there are draining streams, even if there are no open streams.

net/quic/quic_chromium_client_session.h

 // Copyright (c) 2012 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.
 //
 // A client specific QuicSession subclass.  This class owns the underlying
 // QuicConnection and QuicConnectionHelper objects.  The connection stores
 // a non-owning pointer to the helper so this session needs to ensure that
 // the helper outlives the connection.
 
 #ifndef NET_QUIC_QUIC_CHROMIUM_CLIENT_SESSION_H_
@@ skipping 169 matching lines @@
   void OnProofValid(const QuicCryptoClientConfig::CachedState& cached) override;
   void OnProofVerifyDetailsAvailable(
       const ProofVerifyDetails& verify_details) override;
 
   // QuicConnectionVisitorInterface methods:
   void OnConnectionClosed(QuicErrorCode error,
                           const std::string& error_details,
                           ConnectionCloseSource source) override;
   void OnSuccessfulVersionNegotiation(const QuicVersion& version) override;
   void OnPathDegrading() override;
+  bool HasOpenDynamicStreams() const override;

[Ian Swett, 2016/06/20 22:51:01]

Maybe add a comment or TODO about the slightly non-standard behavior?

 
   // QuicChromiumPacketReader::Visitor methods:
   void OnReadError(int result, const DatagramClientSocket* socket) override;
   bool OnPacket(const QuicReceivedPacket& packet,
                 IPEndPoint local_address,
                 IPEndPoint peer_address) override;
 
   // Gets the SSL connection information.
   bool GetSSLInfo(SSLInfo* ssl_info) const;
 
@@ skipping 154 matching lines @@
   int streams_pushed_count_;
   int streams_pushed_and_claimed_count_;
   base::WeakPtrFactory<QuicChromiumClientSession> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(QuicChromiumClientSession);
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUIC_CHROMIUM_CLIENT_SESSION_H_