Please approve JDK-8060471 for backport to 8u40

[Marcus Lagergren]

Compile time issue because log args were evaluated even with disabled logger, in this case containing an expensive stacktrace.

Webrev: http://cr.openjdk.java.net/~lagergren/8060471/webrev/
CR: https://bugs.openjdk.java.net/browse/JDK-8060471
Review thread: http://mail.openjdk.java.net/pipermail/nashorn-dev/2014-October/003662.html

Regards
Marcus