Remove PrefObserver usages, batch 6.

chrome/browser/ui/prefs/prefs_tab_helper.h

Index: chrome/browser/ui/prefs/prefs_tab_helper.h
diff --git a/chrome/browser/ui/prefs/prefs_tab_helper.h b/chrome/browser/ui/prefs/prefs_tab_helper.h
index 5dc8c981bcacee8ff44a5bb86b2917161ee790e9..d3e8caf7f312931d9ecb3dcc3613389c588cbd04 100644
--- a/chrome/browser/ui/prefs/prefs_tab_helper.h
+++ b/chrome/browser/ui/prefs/prefs_tab_helper.h
@@ -7,7 +7,6 @@
 
 #include "base/compiler_specific.h"
 #include "base/prefs/public/pref_change_registrar.h"
-#include "base/prefs/public/pref_observer.h"
 #include "content/public/browser/notification_observer.h"
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/web_contents_user_data.h"
@@ -22,7 +21,6 @@ class WebContents;
 
 // Per-tab class to handle user preferences.
 class PrefsTabHelper : public content::NotificationObserver,
-                       public PrefObserver,
                        public content::WebContentsUserData<PrefsTabHelper> {
  public:
   virtual ~PrefsTabHelper();
@@ -43,9 +41,7 @@ class PrefsTabHelper : public content::NotificationObserver,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
-  // PrefObserver overrides:
-  virtual void OnPreferenceChanged(PrefServiceBase* service,
-                                   const std::string& pref_name) OVERRIDE;
+  void OnPreferenceChanged(const std::string& pref_name);
 
   // Update the WebContents's RendererPreferences.
   void UpdateRendererPreferences();