Destroy store on task runner. That's where all store operations happen.

components/safe_browsing_db/v4_store.h

Index: components/safe_browsing_db/v4_store.h
diff --git a/components/safe_browsing_db/v4_store.h b/components/safe_browsing_db/v4_store.h
index 1b9e4d6ba00b691233d247d30a3b6110bee3e265..9775ee715d1e7e9cde346a12e6386a5d376d865c 100644
--- a/components/safe_browsing_db/v4_store.h
+++ b/components/safe_browsing_db/v4_store.h
@@ -176,6 +176,10 @@ class V4Store {
 
   std::string DebugString() const;
 
+  // Schedules the destruction of the V4Store object pointed to by |v4_store|,
+  // on the task runner.
+  static void Destroy(std::unique_ptr<V4Store> v4_store);
+
   // Reads the store file from disk and populates the in-memory representation
   // of the hash prefixes.
   void Initialize();