[net] Connect DNS signals to re-fetching PAC script.

net/proxy/proxy_service.cc

Index: net/proxy/proxy_service.cc
diff --git a/net/proxy/proxy_service.cc b/net/proxy/proxy_service.cc
index d5c7787731494d8b1fc9135d8cc216fe3fedfb28..9989b8221cdc09944ce3e14622d3d088851b6f7e 100644
--- a/net/proxy/proxy_service.cc
+++ b/net/proxy/proxy_service.cc
@@ -867,6 +867,7 @@ ProxyService::ProxyService(ProxyConfigService* config_service,
       stall_proxy_auto_config_delay_(TimeDelta::FromMilliseconds(
           kDelayAfterNetworkChangesMs)) {
   NetworkChangeNotifier::AddIPAddressObserver(this);
+  NetworkChangeNotifier::AddDNSObserver(this);
   ResetConfigService(config_service);
 }
 
@@ -1022,6 +1023,7 @@ int ProxyService::TryToCompleteSynchronously(const GURL& url,
 
 ProxyService::~ProxyService() {
   NetworkChangeNotifier::RemoveIPAddressObserver(this);
+  NetworkChangeNotifier::RemoveDNSObserver(this);
   config_service_->RemoveObserver(this);
 
   // Cancel any inprogress requests.
@@ -1481,6 +1483,10 @@ void ProxyService::OnIPAddressChanged() {
     ApplyProxyConfigIfAvailable();
 }
 
+void ProxyService::OnDNSChanged() {
+  OnIPAddressChanged();
+}
+
 SyncProxyServiceHelper::SyncProxyServiceHelper(MessageLoop* io_message_loop,
                                                ProxyService* proxy_service)
     : io_message_loop_(io_message_loop),