[net/dns] Isolate DnsConfigWatcher from DnsConfigService.

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_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/observer_list_threadsafe.h"
+#include "base/synchronization/lock.h"
 #include "net/base/net_export.h"
 
 namespace net {
 
 class NetworkChangeNotifierFactory;
 
+namespace internal {
+class DnsConfigWatcher;
+}
+
 // NetworkChangeNotifier monitors the system for network changes, and notifies
 // registered observers of those events.  Observers may register on any thread,
 // and will be called back on the thread from which they registered.
 // NetworkChangeNotifiers are threadsafe, though they must be created and
 // destroyed on the same thread.
 class NET_EXPORT NetworkChangeNotifier {
  public:
   // Flags which are ORed together to form |detail| in OnDNSChanged.
   enum {
     // The DNS configuration (name servers, suffix search) has changed.
     CHANGE_DNS_SETTINGS = 1 << 0,
     // The HOSTS file has changed.
     CHANGE_DNS_HOSTS = 1 << 1,
-    // Computer name has changed.
-    CHANGE_DNS_LOCALHOST = 1 << 2,
+    // The watcher has started.
+    CHANGE_DNS_WATCH_STARTED = 1 << 2,
+    // The watcher has failed and will not be available until further notice.
+    CHANGE_DNS_WATCH_FAILED = 1 << 3,
   };
 
   class NET_EXPORT IPAddressObserver {
    public:
     virtual ~IPAddressObserver() {}
 
     // Will be called when the IP address of the primary interface changes.
     // This includes when the primary interface itself changes.
     virtual void OnIPAddressChanged() = 0;
 
@@ skipping 56 matching lines @@
 
   // Returns true if there is currently no internet connection.
   //
   // A return value of |true| is a pretty strong indicator that the user
   // won't be able to connect to remote sites. However, a return value of
   // |false| is inconclusive; even if some link is up, it is uncertain
   // whether a particular connection attempt to a particular remote site
   // will be successfully.
   static bool IsOffline();
 
+  // Returns true if DNS watcher is operational.
+  static bool IsWatchingDNS();
+
   // Like Create(), but for use in tests.  The mock object doesn't monitor any
   // events, it merely rebroadcasts notifications when requested.
   static NetworkChangeNotifier* CreateMock();
 
   // Registers |observer| to receive notifications of network changes.  The
   // thread on which this is called is the thread on which |observer| will be
   // called back with notifications.  This is safe to call if Create() has not
   // been called (as long as it doesn't race the Create() call on another
   // thread), in which case it will simply do nothing.
   static void AddIPAddressObserver(IPAddressObserver* observer);
@@ skipping 10 matching lines @@
   static void RemoveIPAddressObserver(IPAddressObserver* observer);
   static void RemoveOnlineStateObserver(OnlineStateObserver* observer);
   static void RemoveDNSObserver(DNSObserver* observer);
 
   // Allow unit tests to trigger notifications.
   static void NotifyObserversOfIPAddressChangeForTests() {
     NotifyObserversOfIPAddressChange();
   }
 
  protected:
+  friend class internal::DnsConfigWatcher;
+
   NetworkChangeNotifier();
 
   // Broadcasts a notification to all registered observers.  Note that this
   // happens asynchronously, even for observers on the current thread, even in
   // tests.
   static void NotifyObserversOfIPAddressChange();
   static void NotifyObserversOfOnlineStateChange();
   static void NotifyObserversOfDNSChange(unsigned detail);
 
  private:
@@ skipping 17 matching lines @@
     NetworkChangeNotifier* network_change_notifier_;
   };
 
   const scoped_refptr<ObserverListThreadSafe<IPAddressObserver> >
       ip_address_observer_list_;
   const scoped_refptr<ObserverListThreadSafe<OnlineStateObserver> >
       online_state_observer_list_;
   const scoped_refptr<ObserverListThreadSafe<DNSObserver> >
       resolver_state_observer_list_;
 
+  // True iff DNS watchers are operational.
+  // Otherwise, OnDNSChanged might not be issued for future changes.
+  // TODO(szym): This is a temporary interface, consider restarting them.
+  //             http://crbug.com/116139
+  base::Lock watching_dns_lock_;
+  bool watching_dns_;
+
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifier);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NETWORK_CHANGE_NOTIFIER_H_