Need to fix
1. JDK-8185830 <https://bugs.openjdk.java.net/browse/JDK-8185830> ConcurrentSkipListSet.clone() fails with UnsupportedOperationException http://cr.openjdk.java.net/~martin/webrevs/openjdk10/jsr166-integration/ (It would be nice if we could submit a jdk9 backport now instead of waiting)
