[8u40] Approval request for 8057678: Tests for let and const keywords in Nashorn

[Sergey Lugovoy]

Please approve backport of JDK-8057678: Tests for let and const keywords 
in Nashorn

bug: https://bugs.openjdk.java.net/browse/JDK-8057678
JEP:  https://bugs.openjdk.java.net/browse/JDK-8046038
webrev: http://cr.openjdk.java.net/~avstepan/slugovoy/8057678/webrev.00/
Thread : 
http://mail.openjdk.java.net/pipermail/nashorn-dev/2014-September/003401.html
changeset: http://hg.openjdk.java.net/jdk9/dev/nashorn/rev/884a8ffb6038
8u40 webrev is same as jdk9 webrev

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Thanks,
Sergey