IndexedDB: Recycle cursor objects when calling continue().

content/browser/in_process_webkit/indexed_db_dispatcher_host.cc

Index: content/browser/in_process_webkit/indexed_db_dispatcher_host.cc
diff --git a/content/browser/in_process_webkit/indexed_db_dispatcher_host.cc b/content/browser/in_process_webkit/indexed_db_dispatcher_host.cc
index 747a856555bbf5e6b100dd0c10455e01af9847ac..a3da985899edab47df34e6f4cb7f454378c7cd08 100644
--- a/content/browser/in_process_webkit/indexed_db_dispatcher_host.cc
+++ b/content/browser/in_process_webkit/indexed_db_dispatcher_host.cc
@@ -951,6 +951,8 @@ void IndexedDBDispatcherHost::CursorDispatcherHost::OnContinue(
   if (!idb_cursor)
     return;
 
+  parent_->pending_cursor_continues_[response_id] = cursor_id;

[michaeln, 2011/10/30 21:54:06]

What if the continue call does not complete successfully? How is the map entry
removed in that case?

[michaeln, 2011/10/31 15:08:18]

Looks like there are two ways in which continue does not succeed...
- the method call below throws an exception by setting *ec to non-zero
- instead of onSuccessCursorContinue() eventually being called,
onSuccess(nullValue()) is called.

Instead of holding this extra state in a separate map entry, have you considered
stuffing the required state into the  IndexedDBCallbacks<WebIDBCursor> instance
so that it knows what cursor_id its dealing with and there are no extra map
entries to cleanup on any of the possible return path.

[hans, 2011/10/31 16:11:52]

Right, passing the cursor_id into the callbacks object solves this problem
nicely, so let's do that.

+
   *ec = 0;
   idb_cursor->continueFunction(
       key, new IndexedDBCallbacks<WebIDBCursor>(parent_, response_id), *ec);