I think it's either the synthesizer or maybe the defrag, as the process of defragging is low-key actually executed.
Glad you enjoyed it :)
Ah, you might be able to help some of the leaking by reusing the defrag data rather than generating new one and hoping the browser GC gets around to it (you might be holding a reference somewhere and blocking the cleanup, it's pretty easy to do)
The single defrag blocks that get organized are always the same and get reshuffled, so I'm not sure what I could improve there.
Then they're probably not the ones that are causing the memory leaks, then :P
I don't really know what tools are easily available for traiging the leaks, aside from built in browser ones, unfortunately!
