Controller to receive data and register Sitecore goals

GoalEventController.cs

public class PageEventController : Controller
{
    [System.Web.Mvc.HttpPost]
    public JsonResult RegisterGoal(string goalId, string goalDescription)
    {
        Item eventItem = Sitecore.Context.Database.GetItem(goalId);
        var goal = new PageEventItem(eventItem);

        if (!Tracker.IsActive)
            Tracker.StartTracking();

        Sitecore.Analytics.Model.PageEventData eventData = Tracker.Current.CurrentPage.Register(goal);
        eventData.Data = goal["Description"] + " " + goalDescription;
        Tracker.Current.Interaction.AcceptModifications();

        return Json(new PageEventRequestResult()
        {
            Success = true,
            Message = "Successfully registered goal",
        });
    }
}

Jonathan- Can you please tell me which dll holds this class -PageEventRequestResult