[8u] approval request for 8136544: Call site switching to megamorphic causes incorrect property read

[Sundararajan Athijegannathan]

Please approve.

Bug: https://bugs.openjdk.java.net/browse/JDK-8136544
jdk9 review thread: 
http://mail.openjdk.java.net/pipermail/nashorn-dev/2015-September/005253.html
jdk8u webrev: http://cr.openjdk.java.net/~sundar/8136544/8u/webrev.00/

Backported 'as is' except for modular source layout difference..

Thanks,
-Sundar