Merge "Fix race condition with GC in TransitionManager"

    private static ArrayMap<ViewGroup, ArrayList<Transition>> getRunningTransitions() {

        WeakReference<ArrayMap<ViewGroup, ArrayList<Transition>>> runningTransitions =

                sRunningTransitions.get();

        if (runningTransitions == null || runningTransitions.get() == null) {

            ArrayMap<ViewGroup, ArrayList<Transition>> transitions =

                    new ArrayMap<ViewGroup, ArrayList<Transition>>();

            runningTransitions = new WeakReference<ArrayMap<ViewGroup, ArrayList<Transition>>>(

                    transitions);

            sRunningTransitions.set(runningTransitions);

        if (runningTransitions != null) {

            ArrayMap<ViewGroup, ArrayList<Transition>> transitions = runningTransitions.get();

            if (transitions != null) {

                return transitions;

            }

        }

        return runningTransitions.get();

        ArrayMap<ViewGroup, ArrayList<Transition>> transitions = new ArrayMap<>();

        runningTransitions = new WeakReference<>(transitions);

        sRunningTransitions.set(runningTransitions);

        return transitions;

    }

    private static void sceneChangeRunTransition(final ViewGroup sceneRoot,