function aggregateAndCall(sizes, callback)
        {
            var size = 0;
            var currentX = 0;
            for (var i = 1; i < timestamps.length; ++i) {
                var x = Math.floor((timestamps[i] - startTime) * scaleFactor);
                if (x !== currentX) {
                    if (size)
                        callback(currentX, size);
                    size = 0;
                    currentX = x;
                }
                size += sizes[i];
            }
            callback(currentX, size);
        }
@param {!Array.<number>} sizes
@param {function(number, number):void} callback