Fix issue #5823276: home repaints after full-screen app is exited

Don't consider a window as a candidate for the top fullscreen window
if it is not going to be a candiate for layout.

Also don't consider windows a candidate for layout if their app token
is hidden.  This fixes a transient state where we are preparing to
unhide the window but have not done so yet.

Change-Id: Ife5299ffa003c1df1a4f787b7a2809cbf614ec16