aura: Implement new app list mock.

ash/app_list/app_list_model.cc

Index: ash/app_list/app_list_model.cc
diff --git a/ash/app_list/app_list_model.cc b/ash/app_list/app_list_model.cc
index 8362dd67c69f6f395f0527a09ac14a8ce35fdff4..b9d43e71f5db5effadb9952affc7f2fe804fcd57 100644
--- a/ash/app_list/app_list_model.cc
+++ b/ash/app_list/app_list_model.cc
@@ -12,21 +12,21 @@ AppListModel::AppListModel() {
 AppListModel::~AppListModel() {
 }
 
-void AppListModel::AddGroup(AppListItemGroupModel* group) {
-  groups_.Add(group);
+void AppListModel::AddItem(AppListItemModel* item) {
+  items_.Add(item);
 }
 
-AppListItemGroupModel* AppListModel::GetGroup(int index) {
-  DCHECK(index >= 0 && index < group_count());
-  return groups_.item_at(index);
+AppListItemModel* AppListModel::GetItem(int index) {
+  DCHECK(index >= 0 && index < item_count());
+  return items_.item_at(index);
 }
 
 void AppListModel::AddObserver(ui::ListModelObserver* observer) {
-  groups_.AddObserver(observer);
+  items_.AddObserver(observer);
 }
 
 void AppListModel::RemoveObserver(ui::ListModelObserver* observer) {
-  groups_.RemoveObserver(observer);
+  items_.RemoveObserver(observer);
 }
 
 }  // namespace ash