base

Fix warp animation in keyguard

This fixes a problem where the warp page was remaining onscreen due to a
race between the animation completing and releasing the finger.  The fix
is to track when the page is onscreen or when the warp is still animating
to ensure we hide it when we're done.

Change-Id: Ie53c65d276032da16cd42ec84b23ae812fc7e2eb