Update active touch regions in the nav bar

- Always update active touch regions when the nav bar changes
- Keep touch regions in screen space to match event coords being
  tested on the launcher side

Bug: 161921293
Test: Enable 2 button, ensure we defer recents animation when starting
      from nav buttons.  Also verify with gestural nav + ime dismiss.
Change-Id: Id820a3e64bbbb6a4bcacf369df353cb00fa639e1