Collect all ConnectionAttempts from both sockets in TransportConnectJob.

net/socket/connection_attempts.h

 // Copyright 2015 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_SOCKET_CONNECTION_ATTEMPTS_H_
 #define NET_SOCKET_CONNECTION_ATTEMPTS_H_
 
 #include "net/base/ip_endpoint.h"
 
 namespace net {
 
 // A record of an connection attempt made to connect to a host. Includes TCP
 // and SSL errors, but not proxy connections.
 struct ConnectionAttempt {
   ConnectionAttempt(const IPEndPoint endpoint, int result)
       : endpoint(endpoint), result(result) {}
 
   // Address and port the socket layer attempted to connect to.
   IPEndPoint endpoint;
 
   // Net error indicating the result of that attempt.
   int result;
 };
 
+// Multiple connection attempts, as might be tracked in an HttpTransaction or a
+// URLRequest. Order is insignificant.
 typedef std::vector<ConnectionAttempt> ConnectionAttempts;
 
 }  // namespace net
 
 #endif  // NET_SOCKET_CONNECTION_ATTEMPTS_H_