Remove content::NotificationObserver dependency from most Prefs code.

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

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_NTP_NTP_LOGIN_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_NTP_NTP_LOGIN_HANDLER_H_
 
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_ui_message_handler.h"
 
 class Profile;
 
 // The NTP login handler currently simply displays the current logged in
 // username at the top of the NTP (and update itself when that changes).
 // In the future it may expand to allow users to login from the NTP.
 class NTPLoginHandler : public content::WebUIMessageHandler,
-                        public content::NotificationObserver {
+                        public content::NotificationObserver,
+                        public PrefObserver {
  public:
   NTPLoginHandler();
   virtual ~NTPLoginHandler();
 
   // WebUIMessageHandler interface
   virtual void RegisterMessages() OVERRIDE;
 
   // content::NotificationObserver interface
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver interface
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // Returns true if the login handler should be shown in a new tab page
   // for the given |profile|. |profile| must not be NULL.
   static bool ShouldShow(Profile* profile);
 
   // Registers values (strings etc.) for the page.
   static void GetLocalizedValues(Profile* profile, DictionaryValue* values);
 
  private:
   // User actions while on the NTP when clicking on or viewing the sync promo.
   enum NTPSignInPromoBuckets {
@@ skipping 24 matching lines @@
   void HandleShowAdvancedLoginUI(const ListValue* args);
 
   // Internal helper method
   void UpdateLogin();
 
   StringPrefMember username_pref_;
   content::NotificationRegistrar registrar_;
 };
 
 #endif  // CHROME_BROWSER_UI_WEBUI_NTP_NTP_LOGIN_HANDLER_H_