[w3c/webcomponents] Need a callback for when children changed or parser finished parsing children (#809)

There appears to be a strong desire for having some callback when the parser finishes parsing children or when a new child is inserted or an old child is removed.

Previously, children changed callback was deemed too expensive but I'm not certain that would necessarily be the case given all major browser engines (Blink, Gecko, and WebKit) have builtin mechanism to listen to children changes.

I think we should consider adding this callback once for all. As much as I'd like to make sure custom elements people write are good, developer ergonomics here is quite terrible, and people are resorting very awkward workarounds like attaching mutation observers everywhere, which is arguably far slower.

-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/809