aura: Implement new app list mock.

ash/app_list/app_list_model.h

Index: ash/app_list/app_list_model.h
diff --git a/ash/app_list/app_list_model.h b/ash/app_list/app_list_model.h
index bb797a16e4f6a0787842c21a3b4ff4ab3b10bf8e..c8eda856f76d035e167883a7630c490469bf8090 100644
--- a/ash/app_list/app_list_model.h
+++ b/ash/app_list/app_list_model.h
@@ -6,7 +6,7 @@
 #define ASH_APP_LIST_APP_LIST_MODEL_H_
 #pragma once
 
-#include "ash/app_list/app_list_item_group_model.h"
+#include "ash/app_list/app_list_item_model.h"
 #include "base/basictypes.h"
 #include "ash/ash_export.h"
 #include "ui/base/models/list_model.h"
@@ -17,21 +17,23 @@ namespace ash {
 // which in turn owns a list of AppListItemModels.
 class ASH_EXPORT AppListModel {
  public:
+  typedef ui::ListModel<AppListItemModel> Items;
+
   AppListModel();
   virtual ~AppListModel();
 
-  void AddGroup(AppListItemGroupModel* group);
-  AppListItemGroupModel* GetGroup(int index);
+  void AddItem(AppListItemModel* item);
+  AppListItemModel* GetItem(int index);
 
   void AddObserver(ui::ListModelObserver* observer);
   void RemoveObserver(ui::ListModelObserver* observer);
 
-  int group_count() const {
-    return groups_.item_count();
+  int item_count() const {
+    return items_.item_count();
   }
 
  private:
-  ui::ListModel<AppListItemGroupModel> groups_;
+  Items items_;
 
   DISALLOW_COPY_AND_ASSIGN(AppListModel);
 };