Small: Use a weak pointer for callbacks to V4LocalDatabaseManager

components/safe_browsing_db/v4_local_database_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_SAFE_BROWSING_DB_V4_LOCAL_DATABASE_MANAGER_H_
 #define COMPONENTS_SAFE_BROWSING_DB_V4_LOCAL_DATABASE_MANAGER_H_
 
 // A class that provides the interface between the SafeBrowsing protocol manager
 // and database that holds the downloaded updates.
 
 #include <memory>
 
+#include "base/memory/weak_ptr.h"
 #include "components/safe_browsing_db/database_manager.h"
 #include "components/safe_browsing_db/hit_report.h"
 #include "components/safe_browsing_db/v4_database.h"
 #include "components/safe_browsing_db/v4_get_hash_protocol_manager.h"
 #include "components/safe_browsing_db/v4_protocol_manager_util.h"
 #include "components/safe_browsing_db/v4_update_protocol_manager.h"
 #include "url/gurl.h"
 
 using content::ResourceType;
 
@@ skipping 205 matching lines @@
   // The sequenced task runner for running safe browsing database operations.
   scoped_refptr<base::SequencedTaskRunner> task_runner_;
 
   // The database that manages the stores containing the hash prefix updates.
   // All writes to this variable must happen on the IO thread only.
   std::unique_ptr<V4Database> v4_database_;
 
   // The protocol manager that downloads the hash prefix updates.
   std::unique_ptr<V4UpdateProtocolManager> v4_update_protocol_manager_;
 
+  base::WeakPtrFactory<V4LocalDatabaseManager> weak_factory_;
+
   friend class base::RefCountedThreadSafe<V4LocalDatabaseManager>;
   DISALLOW_COPY_AND_ASSIGN(V4LocalDatabaseManager);
 };  // class V4LocalDatabaseManager
 
 }  // namespace safe_browsing
 
 #endif  // COMPONENTS_SAFE_BROWSING_DB_V4_LOCAL_DATABASE_MANAGER_H_