Use PrefChangeRegistrar everywhere

chrome/browser/background_mode_manager.cc

Index: chrome/browser/background_mode_manager.cc
diff --git a/chrome/browser/background_mode_manager.cc b/chrome/browser/background_mode_manager.cc
index 01a9a36bf6b8d0fdc5852ee1af044aa7dcad18ec..b0110a13b58fab779ff41989dceadde6d10e9e61 100644
--- a/chrome/browser/background_mode_manager.cc
+++ b/chrome/browser/background_mode_manager.cc
@@ -163,7 +163,8 @@ BackgroundModeManager::BackgroundModeManager(Profile* profile,
                  NotificationService::AllSources());
 
   // Listen for changes to the background mode preference.
-  profile_->GetPrefs()->AddPrefObserver(prefs::kBackgroundModeEnabled, this);
+  pref_registrar_.Init(profile_->GetPrefs());
+  pref_registrar_.Add(prefs::kBackgroundModeEnabled, this);
 }
 
 BackgroundModeManager::~BackgroundModeManager() {
@@ -172,10 +173,6 @@ BackgroundModeManager::~BackgroundModeManager() {
   // because in an actual running system we'd get an APP_TERMINATING
   // notification before being destroyed.
   EndBackgroundMode();
-  // Manually remove our pref observer so we don't get notified for prefs
-  // changes (have to do it manually because we can't use the registrar for
-  // prefs notifications).
-  profile_->GetPrefs()->RemovePrefObserver(prefs::kBackgroundModeEnabled, this);
 }
 
 bool BackgroundModeManager::IsBackgroundModeEnabled() {