message: Fix resizer/sizer.js mouse event offset calculation
  The event coordinates are document coordinates, so the offset they are
  compared to should also be the document one.
diff: @@ -56,6 +56,18 @@ export default class Sizer {
  return this.vertical ? this.container.offsetTop : this.container.offsetLeft;
  }
  + /** @return {number} container offset to document */
  + _getPageOffset() {
  + let element = this.container;
  + let offset = 0;
  + while (element) {
  + const pos = this.vertical ? element.offsetTop : element.offsetLeft;
  + offset = offset + pos;
  + element = element.offsetParent;
  + }
  + return offset;
  + }
  +
  setItemSize(item, size) {
  if (this.vertical) {
  item.style.height = `${Math.round(size)}px`;
  @@ -80,9 +92,9 @@ export default class Sizer {
  offsetFromEvent(event) {
  const pos = this.vertical ? event.pageY : event.pageX;
  if (this.reverse) {
  - return (this._getOffset() + this.getTotalSize()) - pos;
  + return (this._getPageOffset() + this.getTotalSize()) - pos;
  } else {
  - return pos - this._getOffset();
  + return pos - this._getPageOffset();
  }
  }
  }
  