Review request: 8000659: NPG: ClassCastExceptions are unexpectedly thrown when testing nashorn

[Stefan Karlsson]

http://cr.openjdk.java.net/~stefank/8000659/webrev/

SystemDictionary::always_strong_oops_do() is missing a call to 
invoke_method_table()->oops_do(). 
SystemDictionary::always_strong_oops_do is used during marking when 
ClassUnloading is enabled. Because of this HotSpot fail to mark the 
objects in this table as alive.

StefanK