- Add all changing windows to mResizingWindows when an ActivityStack
is resized.
- Stop calling TaskStack.setBounds if the bounds haven't changed.
- Make moving a task from one stack to another work properly.
- Eliminate unused methods and redundant variables in WindowState and
WindowStateAnimator.
Change-Id: I3a950c777bcc50cdeced150d44423d4d0b38af4a