8151674: STW phases at Concurrent GC should count in PerfCounter
Reviewed-by: jmasa, sla, tschatzl
[attribute Y]
[flow Y]
[attribute W]
[flow W]
[attribute Z]
[flow Z]
[desugar Z]
[desugar W]
[desugar Y]
[generate code Y]
[generate code W]
[generate code Z]