function metadataReceived(timestamp)
        {
            if (!timestamp)
                return;

            var now = Date.now();
            var deadlineMs = now + this.pollPeriodMs;
            var pollData = this._pollDataForSASSURL[sassURL];
            if (pollData) {
                var dataByURL = pollData.dataByURL;
                for (var url in dataByURL)
                    clearTimeout(dataByURL[url].timer);
            }
            pollData = { dataByURL: {}, deadlineMs: deadlineMs, sassTimestamp: timestamp };
            this._pollDataForSASSURL[sassURL] = pollData;
            for (var i = 0; i < cssURLs.length; ++i) {
                pollData.dataByURL[cssURLs[i]] = { previousPoll: now };
                this._pollCallback(cssURLs[i], sassURL, false);
            }
        }
@param {?Date} timestamp
@this {WebInspector.SASSSourceMapping}