Commented Issue: [CORS] Make System.Web.Http.Cors.Tracing.TraceCategories public [963]

System.Web.Http.Tracing.TraceCategories is public, so should be CORS.

It allows easier tracing code when filtering category is needed.
Comments: Fixed by: https://aspnetwebstack.codeplex.com/SourceControl/changeset/d7838ac0de155755039b1474feea94669c8720ca