function convertFromParentRect(parentBoundingRect, parentIntersectionRect) {
    var top = parentIntersectionRect.top - parentBoundingRect.top
    var left = parentIntersectionRect.left - parentBoundingRect.left
    return {
      top: top,
      left: left,
      height: parentIntersectionRect.height,
      width: parentIntersectionRect.width,
      bottom: top + parentIntersectionRect.height,
      right: left + parentIntersectionRect.width,
    }
  }
Inverts the intersection and bounding rect from the parent (frame) BCR to
the local BCR space.
@param {DOMRect|ClientRect} parentBoundingRect The parent's bound client rect.
@param {DOMRect|ClientRect} parentIntersectionRect The parent's own intersection rect.
@return {ClientRect} The local root bounding rect for the parent's children.