Bind this to custom attribute converter methods

[nebarf]

Fixes #3108

[changeset-bot]

🦋 Changeset detected

Latest commit: b3ab89f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@lit/reactive-element	Patch
lit	Patch

Not sure what this means? Click here to learn what changesets are.

Click here if you're a maintainer who wants to add another changeset to this PR

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[justinfagnani]

Thanks for the fix @nebarf !

I made some comments around creating fewer short-lived function objects due to Function.bind() when setting properties/attributes.

A bigger change that we should consider outside of this fix (I think) would be to do the toAttribute/fromAttribute determination in createProperty() so it's done once per class, not on every property set. cc @sorvell

[justinfagnani]

Thanks for the additional review @augustjk

@nebarf with those comments addressed this looks great!

[augustjk]

Awesome, thank you! I just went ahead and combined the changeset files together which is our preferred way.

[justinfagnani]

LGTM!