Move Singleton and related structs to namespace base

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 <map>
 #include <string>
 
 #include "base/memory/ref_counted.h"
 
-template<typename T> struct DefaultSingletonTraits;
-
 class PrintPreviewDataStore;
 
 namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
 class RefCountedBytes;
 }
 
 // PrintPreviewDataService manages data stores for chrome://print requests.
 // It owns the data store object and is responsible for freeing it.
 class PrintPreviewDataService {
  public:
   static PrintPreviewDataService* GetInstance();
 
   // Get the data entry from PrintPreviewDataStore. |index| is zero-based or
@@ skipping 11 matching lines @@
   void SetDataEntry(int32_t preview_ui_id, int index,
                     const base::RefCountedBytes* data);
 
   // Remove the corresponding PrintPreviewUI entry from the map.
   void RemoveEntry(int32_t preview_ui_id);
 
   // Returns the available draft page count.
   int GetAvailableDraftPageCount(int32_t preview_ui_id);
 
  private:
-  friend struct DefaultSingletonTraits<PrintPreviewDataService>;
+  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>>;
 
   PrintPreviewDataService();
   virtual ~PrintPreviewDataService();
 
   PreviewDataStoreMap data_store_map_;
 
   DISALLOW_COPY_AND_ASSIGN(PrintPreviewDataService);
 };
 
 #endif  // CHROME_BROWSER_PRINTING_PRINT_PREVIEW_DATA_SERVICE_H_