Use PrefChangeRegistrar everywhere

chrome/browser/dom_ui/ntp_resource_cache.cc

Index: chrome/browser/dom_ui/ntp_resource_cache.cc
diff --git a/chrome/browser/dom_ui/ntp_resource_cache.cc b/chrome/browser/dom_ui/ntp_resource_cache.cc
index 600710f314a0dff78f5648d9fbf52372a3711bdf..bd7ff3758d2306031bc5f8ed87c07153eb2b4a87 100644
--- a/chrome/browser/dom_ui/ntp_resource_cache.cc
+++ b/chrome/browser/dom_ui/ntp_resource_cache.cc
@@ -133,15 +133,9 @@ NTPResourceCache::NTPResourceCache(Profile* profile) : profile_(profile) {
                  NotificationService::AllSources());
 
   // Watch for pref changes that cause us to need to invalidate the HTML cache.
-  PrefService* pref_service = profile_->GetPrefs();
-  pref_service->AddPrefObserver(prefs::kShowBookmarkBar, this);
-  pref_service->AddPrefObserver(prefs::kNTPShownSections, this);
-}
-
-NTPResourceCache::~NTPResourceCache() {
-  PrefService* pref_service = profile_->GetPrefs();
-  pref_service->RemovePrefObserver(prefs::kShowBookmarkBar, this);
-  pref_service->RemovePrefObserver(prefs::kNTPShownSections, this);
+  pref_change_registrar_.Init(profile_->GetPrefs());
+  pref_change_registrar_.Add(prefs::kShowBookmarkBar, this);
+  pref_change_registrar_.Add(prefs::kNTPShownSections, this);
 }
 
 RefCountedBytes* NTPResourceCache::GetNewTabHTML(bool is_off_the_record) {