* Returns the given action when there is no current application.
     */
    <T> Action<T> reapplyCurrentLater(Action<T> action);

    /**
     * Returns details of the current application, if any.
     */
    @Nullable
    Application current();

    /**

        currentApplication.set(null);
        try {
            runnable.run();
        } finally {
            currentApplication.set(current);
        }
    }

    @Override
    public <T> Action<T> reapplyCurrentLater(final Action<T> action) {
        final CurrentApplication current = currentApplication.get();
        if (current == null) {
            return action;
        }
        return current.reapplyLater(action);
    }