Ignore accessibility overlays during visible window computation

Previously, the conditional for checking the layer type before
accounting for the window bounds was incorrectly inverted, but
we can simplify by just skipping accessibility overlay windows
completely.

BUG: 18358878
BUG: 18359820
BUG: 18359788
Change-Id: I9ba1e43a0fef4fa40693bd8c7e883c2ef45b4c4d