Fix NSPasteboard leaks.

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_
 
-#import "base/mac/scoped_nsobject.h"
 #include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#import "ui/base/clipboard/clipboard_util_mac.h"
 #include "ui/base/dragdrop/os_exchange_data.h"
 
 @class NSPasteboard;
 
 namespace ui {
+class UniquePasteboard;
 
 // OSExchangeData::Provider implementation for Mac.
 class UI_BASE_EXPORT OSExchangeDataProviderMac
     : public OSExchangeData::Provider {
  public:
   OSExchangeDataProviderMac();
-  explicit OSExchangeDataProviderMac(NSPasteboard* pasteboard);
   ~OSExchangeDataProviderMac() override;
 
   // Overridden from OSExchangeData::Provider:
   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,
                       GURL* url,
                       base::string16* title) const override;
   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;
 
  private:
-  base::scoped_nsobject<NSPasteboard> pasteboard_;
+  explicit OSExchangeDataProviderMac(scoped_refptr<ui::UniquePasteboard>);
+  scoped_refptr<ui::UniquePasteboard> pasteboard_;
 
   DISALLOW_COPY_AND_ASSIGN(OSExchangeDataProviderMac);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_DRAGDROP_OS_EXCHANGE_DATA_PROVIDER_MAC_H_