While using flex app profiling / performance profile, I found out that a lot of cumulative time (>70%) was spent on [tincan] method. After some googling it revealed it is time processing RTMP messages. It includes FMS video/audio traffic, rtmp data services, and remote shared object synchronization.
Tincan used to be the code name of Flash Communication Server 1.0, now known as Flash Media Server.
There are also some more methods logged: [pre-render], [mouseEvent], [enterFrameEvent], [mark], [abc-decode], [verify], [render], [reap], [io], [all-complete], [avm1], [builtins], [execute-queued], [generate], [newclass], [openEvent], [sweep] … unknown for me for now.