Don't account for floating window region in nav bar touchable region

- It's only needed for the deferred gesture region, normally not an
  issue, but b/184914153 causes the layers to be incorrect which
  causes the button to not be touchable because the nav bar is also
  touchable in that region.

Bug: 184914153
Test: Dump touchable region of nav bar window while overlay is showing
      and ensure it's not accounted for
Change-Id: I6cfc0330469ecd53991694dc62118141f9e1ae48