Fix System.hidden detection on Android.
Fix System.hidden detection on Android.

And possibly iOS. The throttle event actually was getting fired, but
only when the app resumed, which was kinda useless.

Disar/flambe,weilitao/flambe,playedonline/flambe,markknol/flambe,aduros/flambe,mikedotalmond/flambe,weilitao/flambe,markknol/flambe,mikedotalmond/flambe,Disar/flambe,aduros/flambe,Disar/flambe,mikedotalmond/flambe,playedonline/flambe,aduros/flambe,Disar/flambe,mikedotalmond/flambe,aduros/flambe,markknol/flambe,playedonline/flambe,weilitao/flambe,weilitao/flambe,playedonline/flambe