Use ChromeLauncherControllerImpl::GetItem; cleanup.

chrome/browser/ui/ash/launcher/chrome_launcher_controller.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 CHROME_BROWSER_UI_ASH_LAUNCHER_CHROME_LAUNCHER_CONTROLLER_H_
 #define CHROME_BROWSER_UI_ASH_LAUNCHER_CHROME_LAUNCHER_CONTROLLER_H_
 
 #include <memory>
 #include <string>
 #include <vector>
@@ skipping 67 matching lines @@
   ~ChromeLauncherController() override;
 
   // Initializes this ChromeLauncherController.
   virtual void Init() = 0;
 
   // Creates a new app item on the shelf for |controller|.
   virtual ash::ShelfID CreateAppLauncherItem(LauncherItemController* controller,
                                              const std::string& app_id,
                                              ash::ShelfItemStatus status) = 0;
 
-  // A helper to get the shelf item with the given id, which must be valid.
-  virtual const ash::ShelfItem& GetItem(ash::ShelfID id) const = 0;
+  // Returns the shelf item with the given id, or null if |id| isn't found.
+  virtual const ash::ShelfItem* GetItem(ash::ShelfID id) const = 0;
 
   // Updates the type of an item.
   virtual void SetItemType(ash::ShelfID id, ash::ShelfItemType type) = 0;
 
   // Updates the running status of an item. It will also update the status of
   // browsers shelf item if needed.
   virtual void SetItemStatus(ash::ShelfID id, ash::ShelfItemStatus status) = 0;
 
   // Updates the controller associated with id (which should be a shortcut).
   // Takes ownership of |controller|.
@@ skipping 217 matching lines @@
   // An observer that manages the shelf title and icon for settings windows.
   SettingsWindowObserver settings_window_observer_;
 
   // Used to load the images for app items.
   std::vector<std::unique_ptr<AppIconLoader>> app_icon_loaders_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeLauncherController);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_LAUNCHER_CHROME_LAUNCHER_CONTROLLER_H_