adoptChildRenderObject method
Adopt child onto this element's render object at slot (document
order). Subclasses override to attach extra metadata such as flex
factors.
Implementation
void adoptChildRenderObject(RenderBox child, Element childElement, int slot) {
final parentRenderObject = _renderObject;
if (parentRenderObject == null) return;
if (child.parent == parentRenderObject) return;
parentRenderObject.adoptChild(child);
}