Detect domain-specific resolvers on OS X and disable DnsClient in such cases.

net/dns/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/dns/host_resolver_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 2115 matching lines @@
 
   // TODO(szym): Remove once http://crbug.com/137914 is resolved.
   received_dns_config_ = dns_config.IsValid();
 
   num_dns_failures_ = 0;
 
   // We want a new DnsSession in place, before we Abort running Jobs, so that
   // the newly started jobs use the new config.
   if (dns_client_.get()) {
     dns_client_->SetConfig(dns_config);
-    if (dns_config.IsValid())
+    if (dns_client_->GetConfig())
       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
   }
 
   // If the DNS server has changed, existing cached info could be wrong so we
   // have to drop our internal cache :( Note that OS level DNS caches, such
   // as NSCD's cache should be dropped automatically by the OS when
   // resolv.conf changes so we don't need to do anything to clear that cache.
   if (cache_.get())
     cache_->clear();
 
@@ skipping 45 matching lines @@
   }
   dns_client_ = dns_client.Pass();
   if (!dns_client_ || dns_client_->GetConfig() ||
       num_dns_failures_ >= kMaximumDnsFailures) {
     return;
   }
   DnsConfig dns_config;
   NetworkChangeNotifier::GetDnsConfig(&dns_config);
   dns_client_->SetConfig(dns_config);
   num_dns_failures_ = 0;
-  if (dns_config.IsValid())
+  if (dns_client_->GetConfig())
     UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
 }
 
 }  // namespace net