RFR(XS): 8037958: ConcurrentMark::cleanup leaks BitMaps if VerifyDuringGC is enabled

[Mikael Gerdin]

Hi all,

While attempting to track down a memory leak I noticed that G1 leaks two 
BitMap instances per concurrent cycle if VerifyDuringGC is enabled.

BitMap's destructor does not free the backing store because BitMaps are 
commonly passed by value. My suggested fix allocates these BitMaps on the 
VMThread's resource area (VMOperation::evaluate has a ResourceMark).

Bug: https://bugs.openjdk.java.net/browse/JDK-8037958
Webrev: http://cr.openjdk.java.net/~mgerdin/8037958/webrev.0

/Mikael