[net] Add DNS-related signals and NetLog to NetworkChangeNotifier.

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 ec2bb1fed50e97c42be5bf424f01e8e9117f9546..1db267c5b30ccb83a7494efb8fdaa3a90acf1e03 100644
--- a/net/base/network_change_notifier_mac.h
+++ b/net/base/network_change_notifier_mac.h
@@ -14,6 +14,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
+#include "net/base/file_path_watcher_callback.h"
 #include "net/base/network_change_notifier.h"
 #include "net/base/network_config_watcher_mac.h"
 
@@ -24,9 +25,11 @@ class NetworkChangeNotifierMac: public NetworkChangeNotifier {
   NetworkChangeNotifierMac();
   virtual ~NetworkChangeNotifierMac();
 
-  // NetworkChangeNotifier implementation:
+  // NetworkChangeNotifier:
   virtual bool IsCurrentlyOffline() const OVERRIDE;
 
+  virtual bool IsCurrentlyWatchingDNS() const OVERRIDE;
+
  private:
   enum OnlineState {
     UNINITIALIZED = -1,
@@ -66,6 +69,9 @@ class NetworkChangeNotifierMac: public NetworkChangeNotifier {
   void SetDynamicStoreNotificationKeys(SCDynamicStoreRef store);
   void OnNetworkConfigChange(CFArrayRef changed_keys);
 
+  // Called from FilePathWatcherCallback.
+  void OnDNSFileChanged(unsigned detail, bool watch_success);
+
   void SetInitialState();
 
   static void ReachabilityCallback(SCNetworkReachabilityRef target,
@@ -83,6 +89,13 @@ class NetworkChangeNotifierMac: public NetworkChangeNotifier {
   Forwarder forwarder_;
   scoped_ptr<const NetworkConfigWatcherMac> config_watcher_;
 
+  // DNS watchers and state.
+  FilePathWatcherCallback resolv_watcher_;
+  FilePathWatcherCallback hosts_watcher_;
+
+  bool watching_dns_;
+  mutable base::Lock watching_dns_lock_;
+
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifierMac);
 };