Allow OSExchangeData::Provider to be overridden at run time.

ui/base/dragdrop/os_exchange_data_provider_win.h

 // Copyright (c) 2012 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_WIN_H_
 #define UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_WIN_H_
 
 #include <objidl.h>
 #include <shlobj.h>
 #include <stddef.h>
@@ skipping 128 matching lines @@
 
   explicit OSExchangeDataProviderWin(IDataObject* source);
   OSExchangeDataProviderWin();
 
   ~OSExchangeDataProviderWin() override;
 
   IDataObject* data_object() const { return data_.get(); }
   IDataObjectAsyncCapability* async_operation() const { return data_.get(); }
 
   // OSExchangeData::Provider methods.
-  Provider* Clone() const override;
+  std::unique_ptr<Provider> Clone() const override;
   void MarkOriginatedFromRenderer() override;
   bool DidOriginateFromRenderer() const override;
   void SetString(const base::string16& data) override;
   void SetURL(const GURL& url, const base::string16& title) override;
   void SetFilename(const base::FilePath& path) override;
   void SetFilenames(const std::vector<FileInfo>& filenames) override;
   void SetPickledData(const Clipboard::FormatType& format,
                       const base::Pickle& data) override;
   void SetFileContents(const base::FilePath& filename,
                        const std::string& file_contents) override;
@@ skipping 30 matching lines @@
   // Drag image and offset data. Only used for Ash.
   gfx::ImageSkia drag_image_;
   gfx::Vector2d drag_image_offset_;
 
   DISALLOW_COPY_AND_ASSIGN(OSExchangeDataProviderWin);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_WIN_H_