Expire but don't clear HostCache on DNS config change

net/base/network_change_notifier.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.
 
 #ifndef NET_BASE_NETWORK_CHANGE_NOTIFIER_H_
 #define NET_BASE_NETWORK_CHANGE_NOTIFIER_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 381 matching lines @@
   static void RemoveConnectionTypeObserver(ConnectionTypeObserver* observer);
   static void RemoveDNSObserver(DNSObserver* observer);
   static void RemoveNetworkChangeObserver(NetworkChangeObserver* observer);
   static void RemoveMaxBandwidthObserver(MaxBandwidthObserver* observer);
   static void RemoveNetworkObserver(NetworkObserver* observer);
 
   // Allow unit tests to trigger notifications.
   static void NotifyObserversOfIPAddressChangeForTests();
   static void NotifyObserversOfConnectionTypeChangeForTests(
       ConnectionType type);
+  static void NotifyObserversOfDNSChangeForTests();
   static void NotifyObserversOfNetworkChangeForTests(ConnectionType type);
   static void NotifyObserversOfInitialDNSConfigReadForTests();
   static void NotifyObserversOfMaxBandwidthChangeForTests(
       double max_bandwidth_mbps,
       ConnectionType type);
 
   // Enable or disable notifications from the host. After setting to true, be
   // sure to pump the RunLoop until idle to finish any preexisting
   // notifications. To use this, it must must be called before a
   // NetworkChangeNotifier is created.
@@ skipping 168 matching lines @@
 
   // Set true to disable non-test notifications (to prevent flakes in tests).
   static bool test_notifications_only_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifier);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NETWORK_CHANGE_NOTIFIER_H_