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

ui/base/dragdrop/os_exchange_data_provider_mac.h

 // Copyright 2014 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_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_MAC_H_
 #define UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_MAC_H_
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #import "ui/base/clipboard/clipboard_util_mac.h"
@@ skipping 33 matching lines @@
   bool GetFilename(base::FilePath* path) const override;
   bool GetFilenames(std::vector<FileInfo>* filenames) const override;
   bool GetPickledData(const Clipboard::FormatType& format,
                       base::Pickle* data) const override;
   bool HasString() const override;
   bool HasURL(OSExchangeData::FilenameToURLPolicy policy) const override;
   bool HasFile() const override;
   bool HasCustomFormat(const Clipboard::FormatType& format) const override;
   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;
 
   // Returns the data for the specified type in the pasteboard.
   NSData* GetNSDataForType(NSString* type) const;
 
   // Creates an OSExchangeData object from the given NSPasteboard object.
   static std::unique_ptr<OSExchangeData> CreateDataFromPasteboard(
       NSPasteboard* pasteboard);
 
   // Returns an array of pasteboard types that can be supported by
   // OSExchangeData.
   static NSArray* SupportedPasteboardTypes();
 
  private:
   explicit OSExchangeDataProviderMac(scoped_refptr<ui::UniquePasteboard>);
   scoped_refptr<ui::UniquePasteboard> pasteboard_;
 
   // Drag image and offset data.
   gfx::ImageSkia drag_image_;
   gfx::Vector2d cursor_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(OSExchangeDataProviderMac);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_MAC_H_