Remove content::NotificationObserver dependency from most Prefs code.

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

Index: chrome/browser/ui/webui/options/media_galleries_handler.h
diff --git a/chrome/browser/ui/webui/options/media_galleries_handler.h b/chrome/browser/ui/webui/options/media_galleries_handler.h
index 451a37ddaff56754979ca45881a208900ef76da4..7ce549bd9d42ceaaad5eb0cf1fc61ab9fd81f696 100644
--- a/chrome/browser/ui/webui/options/media_galleries_handler.h
+++ b/chrome/browser/ui/webui/options/media_galleries_handler.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_WEBUI_OPTIONS_MEDIA_GALLERIES_HANDLER_H_
 
 #include "base/prefs/public/pref_change_registrar.h"
+#include "base/prefs/public/pref_observer.h"
 #include "chrome/browser/ui/webui/options/options_ui.h"
 #include "content/public/browser/notification_observer.h"
 #include "ui/base/dialogs/select_file_dialog.h"
@@ -14,6 +15,7 @@ namespace options {
 
 // Handles messages related to adding or removing media galleries.
 class MediaGalleriesHandler : public OptionsPageUIHandler,
+                              public PrefObserver,
                               public ui::SelectFileDialog::Listener {
  public:
   MediaGalleriesHandler();
@@ -28,10 +30,9 @@ class MediaGalleriesHandler : public OptionsPageUIHandler,
   virtual void FileSelected(const FilePath& path, int index, void* params)
       OVERRIDE;
 
-  // NotificationObserver implementation.
-  virtual void Observe(int type,
-                       const content::NotificationSource& source,
-                       const content::NotificationDetails& details) OVERRIDE;
+  // PrefObserver implementation.
+  virtual void OnPreferenceChanged(PrefServiceBase* service,
+                                   const std::string& pref_name) OVERRIDE;
 
  private:
   // Handles the "addNewGallery" message (no arguments).