Remove more dead app list code.

chrome/browser/ui/app_list/extension_app_model_builder.h

Index: chrome/browser/ui/app_list/extension_app_model_builder.h
diff --git a/chrome/browser/ui/app_list/extension_app_model_builder.h b/chrome/browser/ui/app_list/extension_app_model_builder.h
index 667f280b420bb0ba2063976479c5645dce2fff7d..577e3f8ae41c2098df4d4eaf235b41431d07d976 100644
--- a/chrome/browser/ui/app_list/extension_app_model_builder.h
+++ b/chrome/browser/ui/app_list/extension_app_model_builder.h
@@ -84,15 +84,9 @@ class ExtensionAppModelBuilder : public AppListModelBuilder,
   // Handles profile prefs changes.
   void OnProfilePreferenceChanged();
 
-  // Handles extension prefs changes.
-  void OnExtensionPreferenceChanged();
-
   // Registrar used to monitor the profile prefs.
   PrefChangeRegistrar profile_pref_change_registrar_;
 
-  // Registrar used to monitor the extension prefs.
-  PrefChangeRegistrar extension_pref_change_registrar_;
-
   // We listen to this to show app installing progress.
   extensions::InstallTracker* tracker_ = nullptr;