[net/dns] Removes locking from DnsConfigServiceWin and adds local computer name.

net/dns/dns_config_service.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/dns/dns_config_service.h"
 
 #include "base/logging.h"
 #include "net/base/ip_endpoint.h"
 
 namespace net {
@@ skipping 82 matching lines @@
   }
 
   have_hosts_ = true;
   if (have_config_)
     OnCompleteConfig();
 }
 
 void DnsConfigService::StartTimer() {
   DCHECK(CalledOnValidThread());
   timer_.Stop();
+
+  // Give it a short timeout to come up with a valid config. Otherwise withdraw
+  // the config from the receiver. The goal is to avoid perceivable network
+  // outage (when using the wrong config) but at the same time avoid
+  // unnecessary Job aborts in HostResolverImpl. The signals come from multiple
+  // sources so it might receive multiple events during a config change.
+
+  // DHCP and user-induced changes are on the order of seconds, so 100ms should
+  // not add perceivable delay. On the other hand, config readers should finish
+  // within 100ms with the rare exception of I/O block or extra large HOSTS.
   const base::TimeDelta kTimeout = base::TimeDelta::FromMilliseconds(100);
+
   timer_.Start(FROM_HERE,
                kTimeout,
                this,
                &DnsConfigService::OnTimeout);
 }
 
 void DnsConfigService::OnTimeout() {
   DCHECK(CalledOnValidThread());
   // Indicate that even if there is no change in On*Read, we will need to
   // update the receiver when the config becomes complete.
   need_update_ = true;
+  // Empty config is considered invalid.
   callback_.Run(DnsConfig());
 }
 
 void DnsConfigService::OnCompleteConfig() {
   timer_.Stop();
   if (need_update_) {
     need_update_ = false;
     callback_.Run(dns_config_);
   }
 }
 
 }  // namespace net