Implement NetworkChangeNotifier::IsCurrentlyOffline() for Mac.

net/base/network_change_notifier_mac.h

Index: net/base/network_change_notifier_mac.h
diff --git a/net/base/network_change_notifier_mac.h b/net/base/network_change_notifier_mac.h
index f46a6666f64b4169a32ac468583b7d9959907ab7..02fc9a561b7c4b5849537bf340b8efdddb9c6c1d 100644
--- a/net/base/network_change_notifier_mac.h
+++ b/net/base/network_change_notifier_mac.h
@@ -7,8 +7,11 @@
 #pragma once
 
 #include <SystemConfiguration/SCDynamicStore.h>
+#include <SystemConfiguration/SCNetworkReachability.h>
 
 #include "base/basictypes.h"
+#include "base/mac/scoped_cftyperef.h"
+#include "base/threading/platform_thread.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/network_config_watcher_mac.h"
 
@@ -47,8 +50,16 @@ class NetworkChangeNotifierMac: public NetworkChangeNotifier {
   void SetDynamicStoreNotificationKeys(SCDynamicStoreRef store);
   void OnNetworkConfigChange(CFArrayRef changed_keys);
 
+  static void ReachabilityCallback(SCNetworkReachabilityRef target,
+                                   SCNetworkConnectionFlags flags,
+                                   void* notifier);
+
   Forwarder forwarder_;
   const NetworkConfigWatcherMac config_watcher_;
+  CFRunLoopRef run_loop_;
+  base::mac::ScopedCFTypeRef<SCNetworkReachabilityRef> reachability_;
+  bool network_reachable_;
+  base::PlatformThreadId notifier_thread_id_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifierMac);
 };