Remove more dead app list code.

chrome/browser/ui/app_list/extension_app_model_builder.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef CHROME_BROWSER_UI_APP_LIST_EXTENSION_APP_MODEL_BUILDER_H_
 #define CHROME_BROWSER_UI_APP_LIST_EXTENSION_APP_MODEL_BUILDER_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 66 matching lines @@
 
   // Initializes the |profile_pref_change_registrar_| and the
   // |extension_pref_change_registrar_| to listen for changes to profile and
   // extension prefs, and call OnProfilePreferenceChanged() or
   // OnExtensionPreferenceChanged().
   void InitializePrefChangeRegistrars();
 
   // 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;
 
   // Dispatches extension lifecycle events.
   std::unique_ptr<LauncherExtensionAppUpdater> app_updater_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionAppModelBuilder);
 };
 
 #endif  // CHROME_BROWSER_UI_APP_LIST_EXTENSION_APP_MODEL_BUILDER_H_