[net] HostResolverImpl + DnsTransaction + DnsConfigService = Asynchronous DNS ready for experiments.

net/dns/dns_transaction.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_DNS_DNS_TRANSACTION_H_
 #define NET_DNS_DNS_TRANSACTION_H_
 #pragma once
 
 #include <string>
 
@@ skipping 20 matching lines @@
 
   // Returns the original |hostname|.
   virtual const std::string& GetHostname() const = 0;
 
   // Returns the |qtype|.
   virtual uint16 GetType() const = 0;
 
   // Starts the transaction. Returns the net error on synchronous failure or
   // ERR_IO_PENDING in which case the result will be passed via the callback.
   virtual int Start() = 0;
+
+  // Returns the net_log for this transaction.

[mmenke, 2012/02/14 18:46:00]

nit:  "BoundNetLog".  |net_log| is a private variable name not defined in this
file.

+  virtual const BoundNetLog& net_log() const = 0;
 };
 
 // Creates DnsTransaction which performs asynchronous DNS search.
 // It does NOT perform caching, aggregation or prioritization of transactions.
 //
 // Destroying the factory does NOT affect any already created DnsTransactions.
 class NET_EXPORT_PRIVATE DnsTransactionFactory {
  public:
   // Called with the response or NULL if no matching response was received.
   // Note that the |GetDottedName()| of the response may be different than the
@@ skipping 20 matching lines @@
   // Creates a DnsTransactionFactory which creates DnsTransactionImpl using the
   // |session|.
   static scoped_ptr<DnsTransactionFactory> CreateFactory(
       DnsSession* session) WARN_UNUSED_RESULT;
 };
 
 }  // namespace net
 
 #endif  // NET_DNS_DNS_TRANSACTION_H_