Review request for backport of JDK-8146274: Thread spinning on WeakHashMap.getEntry() with concurrent use of nashorn

[Hannes Wallnoefer]

Please review backport of JDK-8146274.

Webrev: http://cr.openjdk.java.net/~hannesw/8146274/webrev-8u/
Bug: https://bugs.openjdk.java.net/browse/JDK-8146274

The patch needed a small change because the key type of the listeners 
map changed. Also, the original patch included jjs documentation, which 
is not available in 8u.

Thanks,
Hannes