Delete ash-based code for Windows drag-and-drop graphics.

ui/aura/mus/os_exchange_data_provider_mus.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 UI_AURA_MUS_OS_EXCHANGE_DATA_PROVIDER_MUS_H_
 #define UI_AURA_MUS_OS_EXCHANGE_DATA_PROVIDER_MUS_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 71 matching lines @@
 
 #if defined(USE_AURA)
   void SetHtml(const base::string16& html, const GURL& base_url) override;
   bool GetHtml(base::string16* html, GURL* base_url) const override;
   bool HasHtml() const override;
 #endif
 
 #if defined(USE_AURA) || defined(OS_MACOSX)
   void SetDragImage(const gfx::ImageSkia& image,
                     const gfx::Vector2d& cursor_offset) override;
-  const gfx::ImageSkia& GetDragImage() const override;
-  const gfx::Vector2d& GetDragImageOffset() const override;
+  gfx::ImageSkia GetDragImage() const override;
+  gfx::Vector2d GetDragImageOffset() const override;
 #endif
 
  private:
   // Returns true if |formats_| contains a file format and the file name can be
   // parsed as a URL.
   bool GetFileURL(GURL* url) const;
 
   // Returns true if |formats_| contains a string format and the string can be
   // parsed as a URL.
   bool GetPlainTextURL(GURL* url) const;
 
   // Drag image and offset data.
   gfx::ImageSkia drag_image_;
   gfx::Vector2d drag_image_offset_;
 
   Data mime_data_;
 
   DISALLOW_COPY_AND_ASSIGN(OSExchangeDataProviderMus);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_MUS_OS_EXCHANGE_DATA_PROVIDER_MUS_H_