[net/dns] Isolate DnsConfigWatcher from DnsConfigService.

net/base/network_change_notifier_mac.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_mac.h"
 
 #include <netinet/in.h>
+#include <resolv.h>
+
+#include "base/basictypes.h"
+#include "base/threading/thread.h"
+#include "net/dns/dns_config_watcher.h"
+
+#ifndef _PATH_RESCONF  // Normally defined in <resolv.h>
+#define _PATH_RESCONF "/etc/resolv.conf"
+#endif
 
 namespace net {
 
 static bool CalculateReachability(SCNetworkConnectionFlags flags) {
   bool reachable = flags & kSCNetworkFlagsReachable;
   bool connection_required = flags & kSCNetworkFlagsConnectionRequired;
   return reachable && !connection_required;
 }
 
+class NetworkChangeNotifierMac::DnsWatcherThread : public base::Thread {
+ public:
+  DnsWatcherThread() : base::Thread("NetworkChangeNotifier") {}
+
+  virtual ~DnsWatcherThread() {
+    Stop();
+  }
+
+  virtual void Init() OVERRIDE {
+    watcher_.Init();
+  }
+
+  virtual void CleanUp() OVERRIDE {
+    watcher_.CleanUp();
+  }
+
+ private:
+  internal::DnsConfigWatcher watcher_;
+
+  DISALLOW_COPY_AND_ASSIGN(DnsWatcherThread);
+};
+
 NetworkChangeNotifierMac::NetworkChangeNotifierMac()
     : online_state_(UNINITIALIZED),
       initial_state_cv_(&online_state_lock_),
-      forwarder_(this) {
+      forwarder_(this),
+      dns_watcher_thread_(new DnsWatcherThread()) {
   // Must be initialized after the rest of this object, as it may call back into
   // SetInitialState().
   config_watcher_.reset(new NetworkConfigWatcherMac(&forwarder_));
+  dns_watcher_thread_->StartWithOptions(
+      base::Thread::Options(MessageLoop::TYPE_IO, 0));
 }
 
 NetworkChangeNotifierMac::~NetworkChangeNotifierMac() {
   // Delete the ConfigWatcher to join the notifier thread, ensuring that
   // StartReachabilityNotifications() has an opportunity to run to completion.
   config_watcher_.reset();
 
   // Now that StartReachabilityNotifications() has either run to completion or
   // never run at all, unschedule reachability_ if it was previously scheduled.
   if (reachability_.get() && run_loop_.get()) {
@@ skipping 124 matching lines @@
   {
     base::AutoLock lock(notifier_mac->online_state_lock_);
     old_state = notifier_mac->online_state_;
     notifier_mac->online_state_ = new_state;
   }
   if (old_state != new_state)
     NotifyObserversOfOnlineStateChange();
 }
 
 }  // namespace net