Cancel LayoutTransition animations selectively

A recent change to LayoutTransition caused new layout transitions to
cancel any previously-running animations. This was to handle situations
where a transition adding an item needed transitions removing items to
finish their job first (and vice versa). But canceling *all* running
animations from transitions caused some artifacts, like making the status
bar icons blink or fade in, depending on which one was started last.

The new approach is to cancel just the ones we care about: adding animations
cancel removing animations, and vice versa. Either one cancels 'changing'
animations, which prevents objects from being animated to the old end
locations, since the new transition will animate them to the correct new
end locations.

Change-Id: I68ac351b05365cace6639b6618422395c35c83fd
2 files changed