Remove more dead app list code.

ui/app_list/app_list_item.cc

 // Copyright 2013 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.
 
 #include "ui/app_list/app_list_item.h"
 
 #include "base/logging.h"
 #include "ui/app_list/app_list_item_observer.h"
 
 namespace app_list {
@@ skipping 56 matching lines @@
 }
 
 AppListItem* AppListItem::FindChildItem(const std::string& id) {
   return NULL;
 }
 
 size_t AppListItem::ChildItemCount() const {
   return 0;
 }
 
-void AppListItem::OnExtensionPreferenceChanged() {}
-
 bool AppListItem::CompareForTest(const AppListItem* other) const {
   return id_ == other->id_ &&
       folder_id_ == other->folder_id_ &&
       name_ == other->name_ &&
       short_name_ == other->short_name_ &&
       GetItemType() == other->GetItemType() &&
       position_.Equals(other->position_);
 }
 
 std::string AppListItem::ToDebugString() const {
@@ skipping 16 matching lines @@
                                       const std::string& short_name) {
   if (name_ == name && short_name_ == short_name)
     return;
   name_ = name;
   short_name_ = short_name;
   for (auto& observer : observers_)
     observer.ItemNameChanged();
 }
 
 }  // namespace app_list