Move inline "done" checkboxing to DiffInline

Summary:
Ref T12616. This updates clicking the "Done" checkbox for the new stuff.

This one is pretty clean since the "Done" checkbox doesn't do too much weird magic.

Test Plan: Clicked the box a few times.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12616

Differential Revision: https://secure.phabricator.com/D17888