RFR (S): 8165858: heapRegionManager is missing volatile qualifier for _claims

[Erik Österlund]

Hi,

This bug is a split out of the larger JDK-8033552 for adding volatile 
qualifiers to lock-free code.
The motivation is to make our implementation more robust since these 
kind of issues have struck us a few times too many already.

CR: https://bugs.openjdk.java.net/browse/JDK-8165858
Webrev: http://cr.openjdk.java.net/~eosterlund/8165858/webrev.00/

This specific CR handles the lack of volatile qualifiers for the _claims 
field of the HeapRegionClaimer class in the heapRegionManager files. It 
is part of a lock-free protocol for claiming reagions, and should use a 
volatile qualifier to be more robust.

Testing: JPRT

I will need a sponsor to push this.

Thanks,
/Erik