arc: Add InstanceHelper::GetInstanceForMethod()

components/arc/storage_manager/arc_storage_manager.h

 // Copyright 2016 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 COMPONENTS_ARC_STORAGE_MANAGER_ARC_STORAGE_MANAGER_H_
 #define COMPONENTS_ARC_STORAGE_MANAGER_ARC_STORAGE_MANAGER_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 21 matching lines @@
 
   // Gets storage usage of all application's APK, data, and cache size.
   using GetApplicationsSizeCallback =
       base::Callback<void(bool succeeded, arc::mojom::ApplicationsSizePtr)>;
   bool GetApplicationsSize(const GetApplicationsSizeCallback& callback);
 
   // Deletes all applications' cache files.
   bool DeleteApplicationsCache(const base::Callback<void()>& callback);
 
  private:
-  mojom::StorageManagerInstance* GetStorageManagerInstance();
-
   DISALLOW_COPY_AND_ASSIGN(ArcStorageManager);
 };
 
 }  // namespace arc
 
 #endif  // COMPONENTS_ARC_STORAGE_MANAGER_ARC_STORAGE_MANAGER_H_