[net/dns] Isolate DnsConfigWatcher from DnsConfigService.

net/base/network_change_notifier.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/base/network_change_notifier.h"
 #include "net/base/network_change_notifier_factory.h"
 #include "build/build_config.h"
 #if defined(OS_WIN)
 #include "net/base/network_change_notifier_win.h"
 #elif defined(OS_LINUX) && !defined(OS_CHROMEOS)
@@ skipping 63 matching lines @@
 #endif
 }
 
 // static
 bool NetworkChangeNotifier::IsOffline() {
   return g_network_change_notifier &&
          g_network_change_notifier->IsCurrentlyOffline();
 }
 
 // static
+bool NetworkChangeNotifier::IsWatchingDNS() {
+  if (!g_network_change_notifier)
+    return false;
+  base::AutoLock(g_network_change_notifier->watching_dns_lock_);
+  return g_network_change_notifier->watching_dns_;
+}
+
+// static
 NetworkChangeNotifier* NetworkChangeNotifier::CreateMock() {
   return new MockNetworkChangeNotifier();
 }
 
 void NetworkChangeNotifier::AddIPAddressObserver(IPAddressObserver* observer) {
   if (g_network_change_notifier)
     g_network_change_notifier->ip_address_observer_list_->AddObserver(observer);
 }
 
 void NetworkChangeNotifier::AddOnlineStateObserver(
@@ skipping 36 matching lines @@
 
 NetworkChangeNotifier::NetworkChangeNotifier()
     : ip_address_observer_list_(
         new ObserverListThreadSafe<IPAddressObserver>(
             ObserverListBase<IPAddressObserver>::NOTIFY_EXISTING_ONLY)),
       online_state_observer_list_(
         new ObserverListThreadSafe<OnlineStateObserver>(
             ObserverListBase<OnlineStateObserver>::NOTIFY_EXISTING_ONLY)),
       resolver_state_observer_list_(
         new ObserverListThreadSafe<DNSObserver>(
-            ObserverListBase<DNSObserver>::NOTIFY_EXISTING_ONLY)) {
+            ObserverListBase<DNSObserver>::NOTIFY_EXISTING_ONLY)),
+      watching_dns_(false) {
   DCHECK(!g_network_change_notifier);
   g_network_change_notifier = this;
 }
 
+// static
 void NetworkChangeNotifier::NotifyObserversOfIPAddressChange() {
   if (g_network_change_notifier) {
     g_network_change_notifier->ip_address_observer_list_->Notify(
         &IPAddressObserver::OnIPAddressChanged);
   }
 }
 
+// static
 void NetworkChangeNotifier::NotifyObserversOfDNSChange(unsigned detail) {
   if (g_network_change_notifier) {
+    {
+      base::AutoLock(g_network_change_notifier->watching_dns_lock_);
+      if (detail & NetworkChangeNotifier::CHANGE_DNS_WATCH_STARTED) {
+        g_network_change_notifier->watching_dns_ = true;
+      } else if (detail & NetworkChangeNotifier::CHANGE_DNS_WATCH_FAILED) {
+        g_network_change_notifier->watching_dns_ = false;
+      }
+      // Include detail that watch is off to spare the call to IsWatchingDNS.
+      if (!g_network_change_notifier->watching_dns_)
+        detail |= NetworkChangeNotifier::CHANGE_DNS_WATCH_FAILED;

[mmenke, 2012/05/16 16:18:03]

Suggest a:

DCHECK(!(detail & NetworkChangeNotifier::CHANGE_DNS_WATCH_FAILED) ||
       !(detail & NetworkChangeNotifier::CHANGE_DNS_WATCH_STARTED));

Here as a simple sanity check.

+    }
     g_network_change_notifier->resolver_state_observer_list_->Notify(
         &DNSObserver::OnDNSChanged, detail);
   }
 }
 
+// static
 void NetworkChangeNotifier::NotifyObserversOfOnlineStateChange() {
   if (g_network_change_notifier) {
     g_network_change_notifier->online_state_observer_list_->Notify(
         &OnlineStateObserver::OnOnlineStateChanged, !IsOffline());
   }
 }
 
 NetworkChangeNotifier::DisableForTest::DisableForTest()
     : network_change_notifier_(g_network_change_notifier) {
   DCHECK(g_network_change_notifier);
   g_network_change_notifier = NULL;
 }
 
 NetworkChangeNotifier::DisableForTest::~DisableForTest() {
   DCHECK(!g_network_change_notifier);
   g_network_change_notifier = network_change_notifier_;
 }
 
 }  // namespace net