While resizing MacOS suspends the NSDefaultRunLoopMode. So in this
caae we can't post to the system event loop, but must use timers
to restart ourself.

Since the timer itself is scheduled on the NSEventTrackingRunLoopMode
it' also triggers on resize events.

There is still some minor glitch: when resizing too fast some part of
LibreOffice isn't painted, while the left mouse button is down.

Since there isn't any layouting triggered by the mouse up, there has
to be an other inconsistency.

Change-Id: I3ccba78bd23ec8526f21e7b93b027f3d3279f901