[Offline Pages] Updated clearing logic in storage manager.

components/offline_pages/archive_manager.h

Index: components/offline_pages/archive_manager.h
diff --git a/components/offline_pages/archive_manager.h b/components/offline_pages/archive_manager.h
index c81499ee23e87b7423400f6c1bdfd6486bd6b45f..23e29c14e29ad9607273188e9dc172d28788404a 100644
--- a/components/offline_pages/archive_manager.h
+++ b/components/offline_pages/archive_manager.h
@@ -63,6 +63,9 @@ class ArchiveManager {
       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_;