nesting on-load calls

[yoshuawuyts]

It'd be neat if we could nest on-load calls. This is currently not working, but I think it should be possible. The problem is that nested MutationObserver events are incorrectly caught, which causes observer nesting to fail. Unlike https://github.com/shama/on-load/pull/19 I suspect we can make this work without even with the currently globals (e.g. the incrementing counter should help us here).

cc/ @juliangruber

See also

• Example test
• PR attempt at implementing this
• Dat desktop PR discussing this

[yoshuawuyts]

LOL NOPE ALL BETS ARE OFF THIS WORKS ALREADY https://github.com/shama/on-load/blob/master/test.js#L51-L68