SFR 450176 Slow media cut-through.  Don't bother starting a parser (which
we try to stop immediately after) when all we want is the names of the
contained tracks, which doesn't require us to start it.  Not having to
stop the parser (and the underlying source object) saves up to 400ms on
slow machines (depending on thread synchronization).
Also fix some speeling and typso.
Also include something in a sync block that should be synched, rather than
having it outside the block.