Turn off ipv6 when there is no support at startup....

net/base/host_resolver_impl.cc

 // Copyright (c) 2006-2008 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"
 
 #include <cmath>
 #include <deque>
 
 #include "base/basictypes.h"
@@ skipping 35 matching lines @@
 HostResolver* CreateSystemHostResolver(
     NetworkChangeNotifier* network_change_notifier) {
   // Maximum of 50 concurrent threads.
   // TODO(eroman): Adjust this, do some A/B experiments.
   static const size_t kMaxJobs = 50u;
 
   // TODO(willchan): Pass in the NetworkChangeNotifier.
   HostResolverImpl* resolver = new HostResolverImpl(
       NULL, CreateDefaultCache(), network_change_notifier, kMaxJobs);
 
+  if (!HostResolverProc::IPv6Supported())
+    resolver->SetDefaultAddressFamily(net::ADDRESS_FAMILY_IPV4);
   return resolver;
 }
 
 static int ResolveAddrInfo(HostResolverProc* resolver_proc,
                            const std::string& host,
                            AddressFamily address_family,
                            AddressList* out) {
   if (resolver_proc) {
     // Use the custom procedure.
     return resolver_proc->Resolve(host, address_family, out);
@@ skipping 913 matching lines @@
     if (r == req)
       return error;
 
     r->OnComplete(error, AddressList());
   }
 
   return ERR_IO_PENDING;
 }
 
 }  // namespace net