Remove content::NotificationObserver dependency from most Prefs code.

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

Index: chrome/browser/ui/webui/options/browser_options_handler.h
diff --git a/chrome/browser/ui/webui/options/browser_options_handler.h b/chrome/browser/ui/webui/options/browser_options_handler.h
index b67757aa72a631b3855289a5ddea6987cb725675..0488e104196099263f97bd4477f2b8d360ba7693 100644
--- a/chrome/browser/ui/webui/options/browser_options_handler.h
+++ b/chrome/browser/ui/webui/options/browser_options_handler.h
@@ -8,6 +8,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/weak_ptr.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/api/prefs/pref_member.h"
 #include "chrome/browser/api/sync/profile_sync_service_observer.h"
 #include "chrome/browser/printing/cloud_print/cloud_print_setup_handler.h"
@@ -35,6 +36,7 @@ namespace options {
 class BrowserOptionsHandler
     : public OptionsPageUIHandler,
       public CloudPrintSetupHandlerDelegate,
+      public PrefObserver,
       public ProfileSyncServiceObserver,
       public ui::SelectFileDialog::Listener,
       public ShellIntegration::DefaultWebClientObserver,
@@ -74,6 +76,10 @@ class BrowserOptionsHandler
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
+
   // SelectFileDialog::Listener implementation
   virtual void FileSelected(const FilePath& path,
                             int index,