Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/content_settings/content_settings_policy_provider.cc

Index: chrome/browser/content_settings/content_settings_policy_provider.cc
diff --git a/chrome/browser/content_settings/content_settings_policy_provider.cc b/chrome/browser/content_settings/content_settings_policy_provider.cc
index cb24bfd20480c02e37d3a77575e82eae466dcd10..0160b510cd9f619c52b41a9871d7b21a3dc07899 100644
--- a/chrome/browser/content_settings/content_settings_policy_provider.cc
+++ b/chrome/browser/content_settings/content_settings_policy_provider.cc
@@ -422,14 +422,11 @@ void PolicyProvider::ShutdownOnUIThread() {
   prefs_ = NULL;
 }
 
-void PolicyProvider::Observe(int type,
-                             const content::NotificationSource& source,
-                             const content::NotificationDetails& details) {
+void PolicyProvider::OnPreferenceChanged(PrefServiceBase* service,
+                                         const std::string& name) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
-  DCHECK_EQ(chrome::NOTIFICATION_PREF_CHANGED, type);
-  DCHECK_EQ(content::Source<PrefService>(source).ptr(), prefs_);
+  DCHECK_EQ(prefs_, service);
 
-  const std::string& name = *content::Details<std::string>(details).ptr();
   if (name == prefs::kManagedDefaultCookiesSetting) {
     UpdateManagedDefaultSetting(CONTENT_SETTINGS_TYPE_COOKIES);
   } else if (name == prefs::kManagedDefaultImagesSetting) {
@@ -462,10 +459,8 @@ void PolicyProvider::Observe(int type,
              name == prefs::kManagedNotificationsBlockedForUrls) {
     ReadManagedContentSettings(true);
     ReadManagedDefaultSettings();
-  } else {
-    NOTREACHED();
-    return;
   }
+
   NotifyObservers(ContentSettingsPattern(),
                   ContentSettingsPattern(),
                   CONTENT_SETTINGS_TYPE_DEFAULT,