Expire but don't clear HostCache on DNS config change

net/dns/host_resolver_impl.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_impl.h"
 
 #if defined(OS_WIN)
 #include <Winsock2.h>
 #elif defined(OS_POSIX)
 #include <netdb.h>
@@ skipping 2573 matching lines @@
     if (dns_client_->GetConfig()) {
       UMA_HISTOGRAM_BOOLEAN("AsyncDNS.DnsClientEnabled", true);
       // If we just switched DnsClients, restart jobs using new resolver.
       // TODO(pauljensen): Is this necessary?
       config_changed = true;
     }
   }
 
   if (config_changed) {
     // If the DNS server has changed, existing cached info could be wrong so we
-    // have to drop our internal cache :( Note that OS level DNS caches, such
+    // have to expire our internal cache :( Note that OS level DNS caches, such
     // as NSCD's cache should be dropped automatically by the OS when
     // resolv.conf changes so we don't need to do anything to clear that cache.
     if (cache_.get()) {
-      cache_->clear();
+      cache_->OnNetworkChange();
       cache_hit_callbacks_.clear();
     }
 
     // Life check to bail once |this| is deleted.
     base::WeakPtr<HostResolverImpl> self = weak_ptr_factory_.GetWeakPtr();
 
     // Existing jobs will have been sent to the original server so they need to
     // be aborted.
     AbortAllInProgressJobs();
 
@@ skipping 107 matching lines @@
   if (job_)
     job_->CancelRequest(this);
 }
 
 void HostResolverImpl::RequestImpl::ChangeRequestPriority(
     RequestPriority priority) {
   job_->ChangeRequestPriority(this, priority);
 }
 
 }  // namespace net