RFR(XS) : 8038240 : new WB API to get nmethod

[Igor Ignatyev]

Hi all,

Please review the patch which introduces a new WhiteBox method -- byte[] 
getNMethod(). We need this method to write reliable tests for 
JDK-8031321 : 'Support Intel bit manipulation instructions'.

webrev: http://cr.openjdk.java.net/~iignatyev/8038240/webrev.00/
jbs: https://bugs.openjdk.java.net/browse/JDK-8038240
testing: jprt
-- 
Igor