Set correct bounds when docked stack is removed v2

Improved implementation of ag/903691.

Set bounds to null when docked stack is removed and other stacks are
resized to occupy whole display area. It ensures that stacks will have
correct fullscreen status.

Bug: 27857485
Change-Id: I7492ab4cbe2de30e7ccfd5413523c307e11f241d
1 file changed