Updating the focus child means the focus object of the window has changed.
We need to report this to QtGui immediately so that it can e.g. inform the
input context of the new focus object, before widgets reacting to the focus
events start calling update() on the input method.
Change-Id: Ie3f7b835591e71519e3f384c2abdad53242c9736
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
6f504a1cdd