Refactor moveStackWindowsLocked()

The method had multiple inner loops and was a less efficient form of
rebuildAppWindowsLocked(). Rewritten to use rebuildAppWindowsLocked()
and small other refactors.

Item #1 of bug 18088522.

Change-Id: If93fa961922c77c9f0af719e535ae5ca5d30fe59
3 files changed