ScrollableListView isn't focusable

[Hixie]

If I tab through https://tvolkert.github.io/ I never get to the list boxes.

In general, tabbing through https://tvolkert.github.io/, I don't get to the check boxes, the link buttons, any of the widgets under "Lists", half of the widgets in the calendar section, up and down arrows down move between radio buttons, and nothing in the Tables section ends up getting focus.