Remove NOTIFICATION_SYSTEM_SETTING_CHANGED, switch CrosSettings to base::CallbackRegistry.

chrome/browser/chromeos/settings/cros_settings.h

Index: chrome/browser/chromeos/settings/cros_settings.h
diff --git a/chrome/browser/chromeos/settings/cros_settings.h b/chrome/browser/chromeos/settings/cros_settings.h
index e14b2be11752d3474407bf502d6a7e773ea20976..403a5a6e9cde2ac7e1e9d916a95d10334dfe01ac 100644
--- a/chrome/browser/chromeos/settings/cros_settings.h
+++ b/chrome/browser/chromeos/settings/cros_settings.h
@@ -9,12 +9,12 @@
 #include <vector>
 
 #include "base/callback_forward.h"
+#include "base/callback_registry.h"
 #include "base/containers/hash_tables.h"
-#include "base/observer_list.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/threading/non_thread_safe.h"
 #include "chrome/browser/chromeos/settings/cros_settings_names.h"
 #include "chrome/browser/chromeos/settings/cros_settings_provider.h"
-#include "content/public/browser/notification_observer.h"
 
 namespace base {
 class DictionaryValue;
@@ -93,12 +93,11 @@ class CrosSettings : public base::NonThreadSafe {
   bool AddSettingsProvider(CrosSettingsProvider* provider);
   bool RemoveSettingsProvider(CrosSettingsProvider* provider);
 
-  // If the pref at the given |path| changes, we call the observer's Observe
-  // method with NOTIFICATION_SYSTEM_SETTING_CHANGED.
-  void AddSettingsObserver(const char* path,
-                           content::NotificationObserver* obs);
-  void RemoveSettingsObserver(const char* path,
-                              content::NotificationObserver* obs);
+  // Add an observer Callback for changes for the given |path|.
+  typedef base::CallbackRegistry<void>::Subscription ObserverSubscription;
+  scoped_ptr<ObserverSubscription> AddSettingsObserver(
+      const std::string& path,
+      const base::Closure& callback);
 
   // Returns the provider that handles settings with the |path| or prefix.
   CrosSettingsProvider* GetProvider(const std::string& path) const;
@@ -106,7 +105,7 @@ class CrosSettings : public base::NonThreadSafe {
  private:
   friend class CrosSettingsTest;
 
-  // Fires system setting change notification.
+  // Fires system setting change callback.
   void FireObservers(const std::string& path);
 
   // List of ChromeOS system settings providers.
@@ -114,9 +113,7 @@ class CrosSettings : public base::NonThreadSafe {
 
   // A map from settings names to a list of observers. Observers get fired in
   // the order they are added.
-  typedef ObserverList<content::NotificationObserver, true>
-      NotificationObserverList;
-  typedef base::hash_map<std::string, NotificationObserverList*>
+  typedef base::hash_map<std::string, base::CallbackRegistry<void>*>
       SettingsObserverMap;
   SettingsObserverMap settings_observers_;