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

ui/base/dragdrop/os_exchange_data_provider_aura.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_AURA_H_
 #define UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_AURA_H_
 
 #include <map>
 
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/pickle.h"
 #include "ui/base/dragdrop/os_exchange_data.h"
 #include "ui/gfx/geometry/vector2d.h"
 #include "ui/gfx/image/image_skia.h"
 #include "url/gurl.h"
 
 namespace ui {
 
 class Clipboard;
 
 // OSExchangeData::Provider implementation for aura on linux.
 class UI_BASE_EXPORT OSExchangeDataProviderAura
     : public OSExchangeData::Provider {
  public:
   OSExchangeDataProviderAura();
   ~OSExchangeDataProviderAura() override;
 
   // Overridden from OSExchangeData::Provider:
-  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;
   bool GetString(base::string16* data) const override;
   bool GetURLAndTitle(OSExchangeData::FilenameToURLPolicy policy,
@@ skipping 52 matching lines @@
   // For HTML format
   base::string16 html_;
   GURL base_url_;
 
   DISALLOW_COPY_AND_ASSIGN(OSExchangeDataProviderAura);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_AURA_H_