RFR 8251118: BiasedLocking::preserve_marks should not have a HandleMark

[Patricio Chilano]

Hi all,

Please review the following small fix which involves removing the added 
HandleMark in BiasedLocking::preserve_marks():

Bug: https://bugs.openjdk.java.net/browse/JDK-8251118
Webrev: http://cr.openjdk.java.net/~pchilanomate/8251118/v1/webrev/

I've inspected the callers of BiasedLocking::preserve_marks() and they 
all have an assert that the current thread is the VMThread. Since the 
VMThread creates a HandleMark object before executing a VM operation the 
extra HandleMark added in 8249192 is not needed.
I've run tiers1-3 in mach5 with -XX:+UseBiasedLocking and without the 
patch I get several crashes in BiasedLocking::restore_marks(). With the 
patch tests completed successfully.

Thanks,
Patricio