Improve infrastructure for replacing windows.

We need to be more precise when removing the window that is being
replaced. We used to depend on the fact that we can remove it after
the first draw of the new added window. However, due to resizing the
old window might reset its draw state and that will trigger a removal
of that window.

We need to add an information about the window that is replacing the
old one and only when this new window draws itself, we remove the old
one.

This improves the transition after maximizing docked window. This is
a situation where first resize operation finishes and immediately
after we have a replacement operation.

Bug: 24914011
Change-Id: Ia8e5bb7872787e663ba23f26588f9c4db1a5e574