RFR: 8202662: JFR tests fails: Could not find leak with class

[Stefan Johansson]

Hi all,

Please review this fix to avoid failing TLAB allocations when a small 
TLABSize is set.

JBS: https://bugs.openjdk.java.net/browse/JDK-8202662
Webrev: http://cr.openjdk.java.net/~sjohanss/8202662/00/

Summary
A recent change to allow more flexible TLAB sizing was incomplete. When 
setting a small initial size using TLABSize, all TLAB allocations fail 
due to a new check trying to ensure we never give out TLABs smaller than 
MinTLABSize. This check was faulty because of a mix-up between bytes and 
words.

Testing
Locally verified that this fix solves the problems in JFR testing. 
Running the change through Mach5 over night.

Thanks,
Stefan