Expose QWidgetRepaintManager's data structures so that we can write
unit tests, and verify that they are correct after moving opaque
widgets (which triggers the accelerated move code path).
Improve the compareWidget logic to not rely on screen grabbing
(which requires permissions), but instead use QPlatformBackingStore's
toImage function, which is faster and more reliable, and also doesn't
require us to show the UI we want to grab full screen in order to
avoid issues with overlapping windows etc.
Change-Id: Iff2ea419f03a390ab6baca26814fef6ff45f7470
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>
b886a7ca65