Another attempt at issue #5823276: home repaints after full-screen app is exited

This is between the two previous attempts.  I returned the part from the
original that was breaking gallery, but have some new code to detect when
something about the window params has changed that would require a
layout pass to make sure we still do a layout then, even if the window is
not currently visible.

Change-Id: I07745e1f66022583e3076b84cc8bbe8bd2acd48f