Remove PrefObserver usages, batch 10.

chrome/browser/ui/webui/ntp/ntp_login_handler.cc

Index: chrome/browser/ui/webui/ntp/ntp_login_handler.cc
diff --git a/chrome/browser/ui/webui/ntp/ntp_login_handler.cc b/chrome/browser/ui/webui/ntp/ntp_login_handler.cc
index 476150a58fd297a610e04ebcce47122fff38f2a2..94af9f3a0cc9a4df103f8421fec9b025c2f9175b 100644
--- a/chrome/browser/ui/webui/ntp/ntp_login_handler.cc
+++ b/chrome/browser/ui/webui/ntp/ntp_login_handler.cc
@@ -88,7 +88,10 @@ NTPLoginHandler::~NTPLoginHandler() {
 
 void NTPLoginHandler::RegisterMessages() {
   PrefService* pref_service = Profile::FromWebUI(web_ui())->GetPrefs();
-  username_pref_.Init(prefs::kGoogleServicesUsername, pref_service, this);
+  username_pref_.Init(prefs::kGoogleServicesUsername,
+                      pref_service,
+                      base::Bind(&NTPLoginHandler::UpdateLogin,
+                                 base::Unretained(this)));
 
   registrar_.Add(this, chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED,
                  content::NotificationService::AllSources());
@@ -117,12 +120,6 @@ void NTPLoginHandler::Observe(int type,
   }
 }
 
-void NTPLoginHandler::OnPreferenceChanged(PrefServiceBase* service,
-                                          const std::string& pref_name) {
-  if (prefs::kGoogleServicesUsername == pref_name)
-    UpdateLogin();
-}
-
 void NTPLoginHandler::HandleInitializeSyncLogin(const ListValue* args) {
   UpdateLogin();
 }