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

net/base/host_resolver.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_BASE_HOST_RESOLVER_H_
 #define NET_BASE_HOST_RESOLVER_H_
 #pragma once
 
 #include <string>
 
@@ skipping 170 matching lines @@
     size_t max_concurrent_resolves,
     size_t max_retry_attempts,
     NetLog* net_log);
 
 // As above, but the created HostResolver does not use a cache.
 NET_EXPORT HostResolver* CreateNonCachingSystemHostResolver(
     size_t max_concurrent_resolves,
     size_t max_retry_attempts,
     NetLog* net_log);
 
-// Creates a HostResolver implementation that sends actual DNS queries to
-// the specified DNS server and parses response and returns results.
+// As above, but the HostResolver will use the asynchronous DNS client in
+// DnsTransaction, which will be configured using DnsConfigService to match
+// the system DNS settings. If the client fails, the resolver falls back to
+// the global HostResolverProc.
 NET_EXPORT HostResolver* CreateAsyncHostResolver(size_t max_concurrent_resolves,
-                                                 const IPAddressNumber& dns_ip,
+                                                 size_t max_retry_attempts,
                                                  NetLog* net_log);
 }  // namespace net
 
 #endif  // NET_BASE_HOST_RESOLVER_H_