Rename the aura_shell namespace to ash

ash/app_list/app_list_item_group_model.cc

 // Copyright (c) 2011 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 "ash/app_list/app_list_item_group_model.h"
 
-namespace aura_shell {
+namespace ash {
 
 AppListItemGroupModel::AppListItemGroupModel(const std::string& title)
     : title_(title) {
 }
 
 AppListItemGroupModel::~AppListItemGroupModel() {
 }
 
 void AppListItemGroupModel::AddItem(AppListItemModel* item) {
   items_.Add(item);
 }
 
 AppListItemModel* AppListItemGroupModel::GetItem(int index) {
   DCHECK(index >= 0 && index < item_count());
   return items_.item_at(index);
 }
 
-}  // namespace aura_shell
+}  // namespace ash