DNS: Add stubs for persisting data across restarts

net/net_common.gypi

 # Copyright 2015 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.
 
 {
   # This target is included by 'net' target.
   'type': '<(component)',
   'variables': { 'enable_wexit_time_destructors': 1, },
   'dependencies': [
     '../base/base.gyp:base',
@@ skipping 87 matching lines @@
       'sources': ['<@(net_ftp_support_sources)']
     }],
     ['enable_built_in_dns==1', {
       'defines': [
         'ENABLE_BUILT_IN_DNS',
       ]
     }, { # else
       'sources!': [
         'dns/address_sorter_posix.cc',
         'dns/address_sorter_posix.h',
-        'dns/dns_client.cc',
       ],
     }],
     [ 'use_nss_certs == 1', {
         'dependencies': [
           '../build/linux/system.gyp:nss',
         ],
       }, {
         'sources!': [
           'cert/x509_util_nss.h',
         ]
@@ skipping 234 matching lines @@
         ['include', '^proxy/proxy_server_mac\\.cc$'],
       ],
     }],
     ['OS == "ios"', {
       'sources/': [
         ['include', '^cert/test_root_certs_mac\\.cc$'],
       ],
     }],
   ],
 }