[Offline Pages] Updated clearing logic in storage manager.

components/offline_pages/archive_manager.h

 // Copyright 2016 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 COMPONENTS_OFFLINE_PAGES_ARCHIVE_MANAGER_H_
 #define COMPONENTS_OFFLINE_PAGES_ARCHIVE_MANAGER_H_
 
 #include <set>
 #include <vector>
 
@@ skipping 45 matching lines @@
   virtual void GetAllArchives(
       const base::Callback<void(const std::set<base::FilePath>&)>& callback)
       const;
 
   // Gets stats about archive storage, i.e. total archive sizes and free disk
   // space.
   virtual void GetStorageStats(
       const base::Callback<void(const StorageStats& storage_sizes)>& callback)
       const;
 
+ protected:
+  ArchiveManager();
+
  private:
   // Path under which all of the managed archives should be stored.
   base::FilePath archives_dir_;
   // Task runner for running file operations.
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
 };
 
 }  // namespace offline_pages
 
 #endif  // COMPONENTS_OFFLINE_PAGES_ARCHIVE_MANAGER_H_