6861660: OopMapBlock count/size confusion Reviewed-by: tonyp, iveresov

Merge

6871111: G1: remove the concurrent overhead tracker Summary: Removing the concurrent overhead tracker from G1, along with the GC overhead reporter and the G1AccountConcurrentOverhead (both of which rely on the the concurrent overhead tracker). Reviewed-by: iveresov, johnc

6798898: CMS: bugs related to class unloading Summary: Override should_remember_klasses() and remember_klass() as needed. Reviewed-by: ysr, jcoomes