This ensures the taskbar hotseat aligns with the home screen
hotseat, as the latter supports empty cells. When in apps,
the taskbar still collapses the empty cells.
Test: Turn off hotseat predictions, remove some hotseat items,
and ensure the taskbar hotseat spreads out when on home.
Bug: 179886115
Bug: 171917176
Change-Id: I6047c3c5691685edcd8b3519e0305812b1295550