Fetch incremental updates. Store new state in V4Store.

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 e1ccb77edfd143b15ae3994f8404998d573db151..ae1ee65148a337a306aef21edf453cb075860326 100644
--- a/components/safe_browsing_db/v4_local_database_manager.h
+++ b/components/safe_browsing_db/v4_local_database_manager.h
@@ -72,7 +72,8 @@ class V4LocalDatabaseManager : public SafeBrowsingDatabaseManager {
 
   void DatabaseReady(std::unique_ptr<V4Database> v4_database);
 
-  void OnCloseDatabase();
+  // Called when the database has been updated and schedules the next update.
+  void DatabaseUpdated();
 
   // The base directory under which to create the files that contain hashes.
   const base::FilePath base_path_;
@@ -93,6 +94,10 @@ class V4LocalDatabaseManager : public SafeBrowsingDatabaseManager {
   // All writes to this variable must happen on the IO thread only.
   std::unique_ptr<V4Database> v4_database_;
 
+  // Called when the V4Database has finished applying the latest update and is
+  // ready to process next update.
+  DatabaseUpdatedCallback db_updated_callback_;
+
   // The sequenced task runner for running safe browsing database operations.
   scoped_refptr<base::SequencedTaskRunner> task_runner_;