Re: [webcomponents] attributeChangedCallback may be expensive for some attributes (#350)

This is why mutation observers have several configuration options for attributes: https://dom.spec.whatwg.org/#dictdef-mutationobserverinit. `attributeFilter` and `attributeOldValue`. We should probably copy that in some way.

---
Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/350#issuecomment-157301306