Add embedder-specific headers to HTTP CONNECT tunnel request

net/http/http_network_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.
 
 #ifndef NET_HTTP_HTTP_NETWORK_SESSION_H_
 #define NET_HTTP_HTTP_NETWORK_SESSION_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/net_export.h"
 #include "net/dns/host_resolver.h"
 #include "net/http/http_auth_cache.h"
 #include "net/http/http_stream_factory.h"
 #include "net/quic/quic_stream_factory.h"
 #include "net/socket/next_proto.h"
@@ skipping 90 matching lines @@
     bool enable_quic_time_based_loss_detection;
     HostPortPair origin_to_force_quic_on;
     QuicClock* quic_clock;  // Will be owned by QuicStreamFactory.
     QuicRandom* quic_random;
     size_t quic_max_packet_length;
     std::string quic_user_agent_id;
     bool enable_user_alternate_protocol_ports;
     QuicCryptoClientStreamFactory* quic_crypto_client_stream_factory;
     QuicVersionVector quic_supported_versions;
     QuicTagVector quic_connection_options;
+    base::Callback<void(const net::HostPortPair&, HttpRequestHeaders*)>
+        before_proxy_tunnel_request_callback;

[mef, 2014/09/02 17:08:36]

Is there particular reason why it is a separate callback and not part of say
network_delegate?

   };
 
   enum SocketPoolType {
     NORMAL_SOCKET_POOL,
     WEBSOCKET_SOCKET_POOL,
     NUM_SOCKET_POOL_TYPES
   };
 
   explicit HttpNetworkSession(const Params& params);
 
@@ skipping 104 matching lines @@
 
   std::vector<std::string> next_protos_;
   bool enabled_protocols_[NUM_VALID_ALTERNATE_PROTOCOLS];
 
   Params params_;
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_NETWORK_SESSION_H_