base

Fix issue #5367164: memory leak in LayoutTransition

When a transition occurs, layout change listeners are added to the container
being transitioned as well as every container up the view hierarchy. The
parent views were not having those listeners removed, so every time a transition
ran, more listeners would be added. Adding to that, the use of an ArrayList
as the collection to hold the listeners meant that adding duplicate items
would just increase the size of the list. There's now a sanity-check on the add
call to make sure that the listener does not exist already, but more importantly
we remove all listeners added when the transition ends.

Change-Id: I4ea05adf30765db091124065539b0ffd32729b3b