Remove content::NotificationObserver dependency from most Prefs code.

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

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/ui/webui/ntp/ntp_login_handler.h"
 
 #include <string>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 94 matching lines @@
   web_ui()->RegisterMessageCallback("showAdvancedLoginUI",
       base::Bind(&NTPLoginHandler::HandleShowAdvancedLoginUI,
                  base::Unretained(this)));
 }
 
 void NTPLoginHandler::Observe(int type,
                               const content::NotificationSource& source,
                               const content::NotificationDetails& details) {
   if (type == chrome::NOTIFICATION_PROFILE_CACHED_INFO_CHANGED) {
     UpdateLogin();
-  } else if (type == chrome::NOTIFICATION_PREF_CHANGED) {
-    std::string* name = content::Details<std::string>(details).ptr();
-    if (prefs::kGoogleServicesUsername == *name)
-      UpdateLogin();
   } else {
     NOTREACHED();
   }
 }
 
+void NTPLoginHandler::OnPreferenceChanged(PrefServiceBase* service,
+                                          const std::string& pref_name) {
+  if (prefs::kGoogleServicesUsername == pref_name)
+    UpdateLogin();
+}
+
 void NTPLoginHandler::HandleInitializeSyncLogin(const ListValue* args) {
   UpdateLogin();
 }
 
 void NTPLoginHandler::HandleShowSyncLoginUI(const ListValue* args) {
   Profile* profile = Profile::FromWebUI(web_ui());
   std::string username = profile->GetPrefs()->GetString(
       prefs::kGoogleServicesUsername);
   content::WebContents* web_contents = web_ui()->GetWebContents();
   Browser* browser = browser::FindBrowserWithWebContents(web_contents);
@@ skipping 139 matching lines @@
           l10n_util::GetStringUTF16(IDS_SHORT_PRODUCT_NAME)));
   values->SetString("login_status_url",
       hide_sync ? std::string() : chrome::kSyncLearnMoreURL);
   values->SetString("login_status_advanced",
       hide_sync ? string16() :
       l10n_util::GetStringUTF16(IDS_SYNC_PROMO_NTP_BUBBLE_ADVANCED));
   values->SetString("login_status_dismiss",
       hide_sync ? string16() :
       l10n_util::GetStringUTF16(IDS_SYNC_PROMO_NTP_BUBBLE_OK));
 }