[net] Add AsyncDns field trial.

net/base/host_resolver_impl.cc

 // 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.
 
 #include "net/base/host_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 12 matching lines @@
 #include "base/debug/stack_trace.h"
 #include "base/message_loop_proxy.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/stl_util.h"
 #include "base/string_util.h"
 #include "base/threading/worker_pool.h"
 #include "base/time.h"
 #include "base/utf_string_conversions.h"
 #include "base/values.h"
+#include "base/version.h"
 #include "net/base/address_family.h"
 #include "net/base/address_list.h"
 #include "net/base/dns_reloader.h"
 #include "net/base/host_port_pair.h"
 #include "net/base/host_resolver_proc.h"
 #include "net/base/net_errors.h"
 #include "net/base/net_log.h"
 #include "net/base/net_util.h"
 #include "net/dns/address_sorter.h"
 #include "net/dns/dns_client.h"
@@ skipping 2103 matching lines @@
   // |this| may be deleted inside AbortAllInProgressJobs().
   if (self)
     TryServingAllJobsFromHosts();
 }
 
 bool HostResolverImpl::HaveDnsConfig() const {
   return (dns_client_.get() != NULL) && (dns_client_->GetConfig() != NULL);
 }
 
 }  // namespace net