updateChildren(children) {
    if (!this.isFullyClipped || !this._wasFullyClipped) {
      super.updateChildren(children)
    }
  }
@override When fully clipped out of view, skip updating children entirely. We do this by
overriding `updateChildren` instead of using the `shouldUpdateChildren` hook, because the
latter would still traverse the child tree to sync matrices, which we don't need here.
TODO this doesn't work so well when descendants are absolutely positioned or overflow outside our bounds