Use unique_ptrs in PrintPreviewDataService.

chrome/browser/printing/print_preview_data_service.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 CHROME_BROWSER_PRINTING_PRINT_PREVIEW_DATA_SERVICE_H_
 #define CHROME_BROWSER_PRINTING_PRINT_PREVIEW_DATA_SERVICE_H_
 
 #include <stdint.h>
 
 #include <map>
+#include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 
 class PrintPreviewDataStore;
 
 namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
@@ skipping 29 matching lines @@
   // Returns the available draft page count.
   int GetAvailableDraftPageCount(int32_t preview_ui_id) const;
 
  private:
   friend struct base::DefaultSingletonTraits<PrintPreviewDataService>;
 
   // 1:1 relationship between PrintPreviewUI and data store object.
   // Key: PrintPreviewUI ID.
   // Value: Print preview data store object.
   using PreviewDataStoreMap =
-      std::map<int32_t, scoped_refptr<PrintPreviewDataStore>>;
+      std::map<int32_t, std::unique_ptr<PrintPreviewDataStore>>;
 
   PrintPreviewDataService();
   ~PrintPreviewDataService();
 
   PreviewDataStoreMap data_store_map_;
 
   DISALLOW_COPY_AND_ASSIGN(PrintPreviewDataService);
 };
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_PREVIEW_DATA_SERVICE_H_