perf: improve TaskHelpers.Iterate. There's a huge perf penalty for switch threads on completed tasks.
perf: improve TaskHelpers.Iterate. There's a huge perf penalty for switch threads on completed tasks.

congysu/WebApi,LianwMS/WebApi,chimpinano/WebApi,chimpinano/WebApi,scz2011/WebApi,lewischeng-ms/WebApi,abkmr/WebApi,yonglehou/WebApi,lungisam/WebApi,yonglehou/WebApi,abkmr/WebApi,scz2011/WebApi,LianwMS/WebApi,lungisam/WebApi,lewischeng-ms/WebApi,congysu/WebApi