Small: Use a weak pointer for callbacks to V4LocalDatabaseManager

components/safe_browsing_db/v4_local_database_manager.h

Index: components/safe_browsing_db/v4_local_database_manager.h
diff --git a/components/safe_browsing_db/v4_local_database_manager.h b/components/safe_browsing_db/v4_local_database_manager.h
index 53ce02582e84fa26470b41fd31f70ab7eac2f9f2..a5bdef46ae48c68c2802c375f7d8703c4910e09b 100644
--- a/components/safe_browsing_db/v4_local_database_manager.h
+++ b/components/safe_browsing_db/v4_local_database_manager.h
@@ -10,6 +10,7 @@
 
 #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"
@@ -235,6 +236,8 @@ class V4LocalDatabaseManager : public SafeBrowsingDatabaseManager {
   // 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