arc: Add InstanceHelper::GetInstanceForMethod()

chrome/browser/chromeos/arc/arc_wallpaper_service.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 CHROME_BROWSER_CHROMEOS_ARC_ARC_WALLPAPER_SERVICE_H_
 #define CHROME_BROWSER_CHROMEOS_ARC_ARC_WALLPAPER_SERVICE_H_
 
 #include <stdint.h>
 
 #include "ash/common/wallpaper/wallpaper_controller_observer.h"
@@ skipping 30 matching lines @@
   void GetWallpaper(const GetWallpaperCallback& callback) override;
 
   // ImageDecoder::ImageRequest implementation.
   void OnImageDecoded(const SkBitmap& bitmap) override;
   void OnDecodeImageFailed() override;
 
   // WallpaperControllerObserver implementation.
   void OnWallpaperDataChanged() override;
 
  private:
-  mojom::WallpaperInstance* GetWallpaperInstance(uint32_t min_version);
-
   mojo::Binding<mojom::WallpaperHost> binding_;
   DISALLOW_COPY_AND_ASSIGN(ArcWallpaperService);
 };
 
 }  // namespace arc
 
 #endif  // CHROME_BROWSER_CHROMEOS_ARC_ARC_WALLPAPER_SERVICE_H_