hg: jdk9/sandbox/jdk: Sync up Reference.reachabilityFence with latest patch.

[paul.sandoz at oracle.com]

Changeset: a639db1eec37
Author:    psandoz
Date:      2015-12-01 17:01 +0100
URL:       http://hg.openjdk.java.net/jdk9/sandbox/jdk/rev/a639db1eec37

Sync up Reference.reachabilityFence with latest patch.

! src/java.base/share/classes/java/lang/ref/Reference.java
- test/java/lang/ref/ReachabilityFence.java
+ test/java/lang/ref/ReachabilityFenceTest.java