Updated blur interpolation for notification shade

The animation has been updated so 60% of the amount of blur is
controlled by a physics-based animation that it's triggered once the
user starts pulling the notification shade. The other 40% is controlled
by the shade expansion amount.

Bug: 152988192
Test: visual
Change-Id: I3895bff685be60714f19ec2a29d125050c9c2da7