[net/dns] Isolate DnsConfigWatcher from DnsConfigService.

net/base/network_change_notifier_mac.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_MAC_H_
 #define NET_BASE_NETWORK_CHANGE_NOTIFIER_MAC_H_
 #pragma once
 
 #include <SystemConfiguration/SystemConfiguration.h>
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
 #include "base/mac/scoped_cftyperef.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/network_config_watcher_mac.h"
 
 namespace net {
 
 class NetworkChangeNotifierMac: public NetworkChangeNotifier {
  public:
   NetworkChangeNotifierMac();
   virtual ~NetworkChangeNotifierMac();
 
-  // NetworkChangeNotifier implementation:
+  // NetworkChangeNotifier:
   virtual bool IsCurrentlyOffline() const OVERRIDE;
 
  private:
   enum OnlineState {
     UNINITIALIZED = -1,
     OFFLINE = 0,
     ONLINE = 1
   };
 
+  class DnsWatcherThread;
+
   // Forwarder just exists to keep the NetworkConfigWatcherMac API out of
   // NetworkChangeNotifierMac's public API.
   class Forwarder : public NetworkConfigWatcherMac::Delegate {
    public:
     explicit Forwarder(NetworkChangeNotifierMac* net_config_watcher)
         : net_config_watcher_(net_config_watcher) {}
 
     // NetworkConfigWatcherMac::Delegate implementation:
     virtual void Init() OVERRIDE {
       net_config_watcher_->SetInitialState();
@@ skipping 29 matching lines @@
   // the lock is in a valid state when Forwarder::Init is called.
   OnlineState online_state_;
   mutable base::Lock online_state_lock_;
   mutable base::ConditionVariable initial_state_cv_;
   base::mac::ScopedCFTypeRef<SCNetworkReachabilityRef> reachability_;
   base::mac::ScopedCFTypeRef<CFRunLoopRef> run_loop_;
 
   Forwarder forwarder_;
   scoped_ptr<const NetworkConfigWatcherMac> config_watcher_;
 
+  // Thread on which we can run DnsConfigWatcher, which requires TYPE_IO.
+  scoped_ptr<DnsWatcherThread> dns_watcher_thread_;
+
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifierMac);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NETWORK_CHANGE_NOTIFIER_MAC_H_