Switch the status bar color earlier in the all apps transition

-> When LAUNCHER3_GRADIENT_ALL_APPS is true, switch the status / nav bar
   to be dark when the transition is 75% of the way through, since at this point
   the gradient is already substantially under the status bar.

issue 64385775

Change-Id: Ie27b8f2afa404c0b3081a4f17daa92ef4e0472bc