Legacy record timestamp conversion

        function processRecord(recordPayload, parentRecordPayload)
        {
            var startTime = recordPayload.startTime;
            var endTime = recordPayload.endTime;

            // COMPATIBILITY (iOS8): old versions use milliseconds since the epoch, rather
            // than seconds elapsed since timeline capturing started. We approximate the latter by
            // subtracting the start timestamp, as old versions did not use monotonic times.
            if (isNaN(this._legacyFirstRecordTimestamp))
                this._legacyFirstRecordTimestamp = recordPayload.startTime;

            // If the record's start time sems unreasonably large, treat it as a legacy timestamp.
            if (startTime > WebInspector.StartTimeThresholdForLegacyRecordConversion) {
                startTime = (startTime - this._legacyFirstRecordTimestamp) / 1000;
                endTime = isNaN(endTime) ? NaN : (startTime - this._legacyFirstRecordTimestamp) / 1000;
            }