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

net/base/net_log_event_type_list.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.
 
 // NOTE: No header guards are used, since this file is intended to be expanded
 // directly into net_log.h. DO NOT include this file anywhere else.
 
 // In the event of a failure, a many end events will have a |net_error|
 // parameter with the integer error code associated with the failure.  Most
 // of these parameters are not individually documented.
@@ skipping 1609 matching lines @@
 //   {
 //     "new_connection_type": <Type of the new connection>
 //   }
 EVENT_TYPE(NETWORK_CHANGED)
 
 // This event is emitted whenever HostResolverImpl receives a new DnsConfig
 // from the DnsConfigService.
 //   {
 //     "nameservers":                <List of name server IPs>,
 //     "search":                     <List of domain suffixes>,
+//     "unhandled_options":          <See DnsConfig>,
 //     "append_to_multi_label_name": <See DnsConfig>,
 //     "ndots":                      <See DnsConfig>,
 //     "timeout":                    <See DnsConfig>,
 //     "attempts":                   <See DnsConfig>,
 //     "rotate":                     <See DnsConfig>,
 //     "edns0":                      <See DnsConfig>,
 //     "num_hosts":                  <Number of entries in the HOSTS file>
 //   }
 EVENT_TYPE(DNS_CONFIG_CHANGED)
 
@@ skipping 580 matching lines @@
 // more references to the entry remaining.
 EVENT_TYPE(SIMPLE_CACHE_ENTRY_CLOSE_CALL)
 
 // This event is created when the Simple Cache actually starts closing a cache
 // entry.  It contains no parameters.
 EVENT_TYPE(SIMPLE_CACHE_ENTRY_CLOSE_BEGIN)
 
 // This event is created when the Simple Cache finishes a CloseEntry call.  It
 // contains no parameters.
 EVENT_TYPE(SIMPLE_CACHE_ENTRY_CLOSE_END)