DNS: Add stubs for persisting data across restarts

net/dns/host_resolver.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.h"
 
 #include "base/logging.h"
 #include "base/metrics/field_trial.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
@@ skipping 99 matching lines @@
 }
 
 HostCache* HostResolver::GetHostCache() {
   return nullptr;
 }
 
 std::unique_ptr<base::Value> HostResolver::GetDnsConfigAsValue() const {
   return nullptr;
 }
 
+void HostResolver::InitializePersistence(
+    const PersistCallback& persist_callback,
+    std::unique_ptr<const base::Value> old_data) {}
+
 // static
 std::unique_ptr<HostResolver> HostResolver::CreateSystemResolver(
     const Options& options,
     NetLog* net_log) {
   return std::unique_ptr<HostResolver>(new HostResolverImpl(options, net_log));
 }
 
 // static
 std::unique_ptr<HostResolver> HostResolver::CreateDefaultResolver(
     NetLog* net_log) {
   return std::unique_ptr<HostResolver>(
       new HostResolverImpl(Options(), net_log));
 }
 
 HostResolver::HostResolver() {
 }
 
 }  // namespace net