Modality test failed.

To reproduce:
1.execute sanity
2.Windows
3.Modality test
4.try to press any button on the background window, the buttons can be pressed. And according to the modality properties only the new window should be active.

FX build under testing:
http://jfx.us.oracle.com/hudson/job/8u-dev/501/label=linux-arm-30/artifact/