Hi Lim255,
I went through 4.0, 4.1,5.5 API reference but I could not find this class. Also I went through latest VIJAVA environment that I have configured, I did not see this class there as well. Then I went through internal API SDK environment, I could see "PerfCounterInfoInt" is available as internal API. Hence at the moment you can not use this API.
Nonetheless,
As you said, you used this API in past. Reason might be :: that time this API was public. When this API got backed out from public API list is unknown to me but when VMware decided to back out this API from public API, it seems, all of its references are removed too.
Alternately you can go ahead & use "PerfCounterInfo" instead.