This prevents views from drawing over higher z-order views.
Currently this is not an issue in practice, because we use
ForceFlushViewsContentOnly only for the bottom line status spinner, and there
are never views on top of it. However, later in the branch we will use the
mechanism to redraw the inline spinners in panels (e.g. the "Pushing..." status
next to a branch name), and there could be a popup on top of it.
Co-authored-by: Stefan Haller <stefan@haller-berlin.de>
b3deef31ad