It was added for Symbian almost 10 years ago (d7057e7c1f1a), for a somewhat
dubious use-case. The Symbian code is since long gone (ae30d7141), so the
remaining pieces are just adding complexity to the already intricate workings
of the QtWidgets backingstore/painting logic.
Task-number: QTBUG-8697
Change-Id: I82af610a8ac26719c588ac63f06b4501f59b400d
Reviewed-by: Paul Olav Tvete <paul.tvete@qt.io>
(cherry picked from commit 2e0b0be2ce)
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
f4db381169