message: remove resizeobserver code
  seems to cause more harm than good in some cases and we shouldn't need
  it if we get our calls to onHeightChanged in order.
diff: @@ -79,26 +79,6 @@ if (DEBUG_SCROLL) {
  * offset as normal.
  */
  -
  -function createTimelineResizeDetector(scrollNode, itemlist, callback) {
  - if (typeof ResizeObserver !== "undefined") {
  - const ro = new ResizeObserver(callback);
  - ro.observe(itemlist);
  - return ro;
  - } else if (typeof IntersectionObserver !== "undefined") {
  - const threshold = [];
  - for (let i = 0; i <= 1000; ++i) {
  - threshold.push(i / 1000);
  - }
  - const io = new IntersectionObserver(
  - callback,
  - {root: scrollNode, threshold},
  - );
  - io.observe(itemlist);
  - return io;
  - }
  -}
  -
  module.exports = React.createClass({
  displayName: 'ScrollPanel',
  @@ -181,12 +161,6 @@ module.exports = React.createClass({
  componentDidMount: function() {
  this.checkScroll();
  -
  - this._timelineSizeObserver = createTimelineResizeDetector(
  - this._getScrollNode(),
  - this.refs.itemlist,
  - () => { this._restoreSavedScrollState(); },
  - );
  },
  componentDidUpdate: function() {
  