app_list: Fix possible out of bounds index.

ui/app_list/test/app_list_test_model.h

 // 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.
 
 #ifndef UI_APP_LIST_TEST_APP_LIST_TEST_MODEL_H_
 #define UI_APP_LIST_TEST_APP_LIST_TEST_MODEL_H_
 
 #include <string>
 
 #include "ui/app_list/app_list_folder_item.h"
@@ skipping 35 matching lines @@
   std::string GetItemName(int id);
 
   // Populate the model with |n| items titled "Item #".
   void PopulateApps(int n);
 
   // Creates and populate a folder with |n| test apps in it.
   AppListFolderItem* CreateAndPopulateFolderWithApps(int n);
 
   AppListFolderItem* CreateAndAddOemFolder(const std::string& id);
 
+  AppListFolderItem* CreateSingleItemFolder(const std::string& folder_id,
+                                            const std::string& item_id);
+
   // Populate the model with an item titled "Item |id|".
   void PopulateAppWithId(int id);
 
   // Get a string of all apps in |model| joined with ','.
   std::string GetModelContent();
 
   // Creates an item with id |id|. Caller owns the result.
   AppListTestItem* CreateItem(const std::string& id);
 
   // Creates and adds an item with id |id| to the model. Returns an unowned
@@ skipping 12 matching lines @@
   int activate_count_;
   AppListItem* last_activated_;
 
   DISALLOW_COPY_AND_ASSIGN(AppListTestModel);
 };
 
 }  // namespace test
 }  // namespace app_list
 
 #endif  // UI_APP_LIST_TEST_APP_LIST_TEST_MODEL_H_