Remove content::NotificationObserver dependency from most Prefs code.

chrome/browser/ui/webui/options/content_settings_handler.h

Index: chrome/browser/ui/webui/options/content_settings_handler.h
diff --git a/chrome/browser/ui/webui/options/content_settings_handler.h b/chrome/browser/ui/webui/options/content_settings_handler.h
index 63a83aead2d6c0c5a8f8bec7e7bdc66b9dd1839e..5aa54be5c6d6a08171a52f04f03c88a30182dbab 100644
--- a/chrome/browser/ui/webui/options/content_settings_handler.h
+++ b/chrome/browser/ui/webui/options/content_settings_handler.h
@@ -10,6 +10,7 @@
 
 #include "base/memory/scoped_ptr.h"
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/pepper_flash_settings_manager.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 #include "chrome/common/content_settings.h"
@@ -23,7 +24,8 @@ class ProtocolHandlerRegistry;
 namespace options {
 
 class ContentSettingsHandler : public OptionsPageUIHandler,
-                               public PepperFlashSettingsManager::Client {
+                               public PepperFlashSettingsManager::Client,
+                               public PrefObserver {
  public:
   ContentSettingsHandler();
   virtual ~ContentSettingsHandler();
@@ -40,6 +42,10 @@ class ContentSettingsHandler : public OptionsPageUIHandler,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // PepperFlashSettingsManager::Client implementation.
   virtual void OnGetPermissionSettingsCompleted(
       uint32 request_id,