function PeriodThrottledDelayer(defaultDelay, minimumPeriod) {
            if (minimumPeriod === void 0) { minimumPeriod = 0; }
            var _this = _super.call(this, defaultDelay) || this;
            _this.minimumPeriod = minimumPeriod;
            _this.periodThrottler = new Throttler();
            return _this;
        }
Similar to the ThrottledDelayer, except it also guarantees that the promise
factory doesn't get called more often than every `minimumPeriod` milliseconds.