This reverts commit fad9555217ce3a657ffc7cba458a0d2622f7a379.
Because it just didn't work. (The views kept aggressively
re-applying their preferred flags every time view attributes
were aggregated.)
We'll pursue the original strategy, like lights out mode in
HC: if you want to tickle this mode, un-set and re-set the
flags (preferably synchronized with the global SystemUI
visibility state as reported by onSystemUiVisibilityChanged
callbacks).
Bug: 5052456
705240631b