I don't think the webworker solution would work for something like this, anything that needed to use anything outside of the workers context would break. It seems like khan's environment is much more restricted, so they can get away with it.
Yep - totally right. It would involve mocking out the entire browser API in a way that would somehow still follow the same codepaths. That said, it could still catch some things. If the web worker errors out, you just completely ignore the errors and just run it anyway. But if it times out, it's (almost) definitely going to time out in the real page too, unless you're waiting for some specific DOM event or something weird.
