Allow stacks to be placed outside of display

When dismissing the docked stack, we animate the divider to position
-12dp, so the full-screen stack is exactly full-screen when the dismiss
animation is done. Previously, this was prevented by window manager.
Allow it to fix the animation.

Change-Id: Iee4505023dc3f6907d56851965b156235f9f97f2
3 files changed