Slide unlock cannot get accessibility focus.

1. There are two overlaid views, one is the GlowPadView and the
   other is the SlidingChallengeLayout. Since the GlowPadView is
   on top of the other view it has to consume the hover events or
   they will be dispatched to the view behind it which results
   the the GlowPadView not getting accessibility focus.

bug:7496770

Change-Id: Iae3b1777e490c56e33560a016fc04a92226bfb66