[15] RFR 8241155: Shenandoah: Traversal GC should mark strong CLD roots when class unloading is enabled

[Zhengyu Gu]

Current traversal GC does not mark strong CLD roots, it seems wrong.

Bug: https://bugs.openjdk.java.net/browse/JDK-8241155
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8241155/webrev.00/

Test:
   hotspot_gc_shenandoah (fastdebug and release)
   tools/javac

Thanks,

-Zhengyu