getSnapshotBeforeUpdate (prevProps) {
    const someItemInserted = Children.count(prevProps.children) > 0 &&
      Children.count(prevProps.children) < Children.count(this.props.children) &&
      this.getFirstChildKey(prevProps) !== this.getFirstChildKey(this.props);
    const pendingChanged = (prevProps.numPending > 0) !== (this.props.numPending > 0);