Replace single-threaded SequencedWorkerPool with base::Thread in WallpaperResizerTest.

components/wallpaper/wallpaper_resizer.h

 // Copyright (c) 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 COMPONENTS_WALLPAPER_WALLPAPER_RESIZER_H_
 #define COMPONENTS_WALLPAPER_WALLPAPER_RESIZER_H_
 
 #include <stdint.h>
 
 #include "base/macros.h"
@@ skipping 20 matching lines @@
 class WALLPAPER_EXPORT WallpaperResizer {
  public:
   // Returns a unique identifier corresponding to |image|, suitable for
   // comparison against the value returned by original_image_id(). If the image
   // is modified, its ID will change.
   static uint32_t GetImageId(const gfx::ImageSkia& image);
 
   WallpaperResizer(const gfx::ImageSkia& image,
                    const gfx::Size& target_size,
                    WallpaperLayout layout,
-                   const scoped_refptr<base::TaskRunner>& task_runner);
+                   scoped_refptr<base::TaskRunner> task_runner);
 
   ~WallpaperResizer();
 
   const gfx::ImageSkia& image() const { return image_; }
   uint32_t original_image_id() const { return original_image_id_; }
   WallpaperLayout layout() const { return layout_; }
 
   // Called on the UI thread to run Resize() on the task runner and post an
   // OnResizeFinished() task back to the UI thread on completion.
   void StartResize();
@@ skipping 24 matching lines @@
   scoped_refptr<base::TaskRunner> task_runner_;
 
   base::WeakPtrFactory<WallpaperResizer> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperResizer);
 };
 
 }  // namespace wallpaper
 
 #endif  // COMPONENTS_WALLPAPER_WALLPAPER_RESIZER_H_