Update NetworkStateNotifier to use message_center.

ash/system/tray/system_tray_notifier.cc

Index: ash/system/tray/system_tray_notifier.cc
diff --git a/ash/system/tray/system_tray_notifier.cc b/ash/system/tray/system_tray_notifier.cc
index fcdb2d6d5bc9e810d3da385a7f3f9643b49b8b35..fde1e7d7efe2f64517f1709fa0d786c78df232dc 100644
--- a/ash/system/tray/system_tray_notifier.cc
+++ b/ash/system/tray/system_tray_notifier.cc
@@ -287,31 +287,6 @@ void SystemTrayNotifier::NotifyUserUpdate() {
 
 #if defined(OS_CHROMEOS)
 
-void SystemTrayNotifier::NotifySetNetworkMessage(
-    NetworkTrayDelegate* delegate,
-    NetworkObserver::MessageType message_type,
-    NetworkObserver::NetworkType network_type,
-    const base::string16& title,
-    const base::string16& message,
-    const std::vector<base::string16>& links) {
-  FOR_EACH_OBSERVER(NetworkObserver,
-                    network_observers_,
-                    SetNetworkMessage(
-                        delegate,
-                        message_type,
-                        network_type,
-                        title,
-                        message,
-                        links));
-}
-
-void SystemTrayNotifier::NotifyClearNetworkMessage(
-    NetworkObserver::MessageType message_type) {
-  FOR_EACH_OBSERVER(NetworkObserver,
-                    network_observers_,
-                    ClearNetworkMessage(message_type));
-}
-
 void SystemTrayNotifier::NotifyRequestToggleWifi() {
   FOR_EACH_OBSERVER(NetworkObserver,
                     network_observers_,