adoptChild method
Called by subclasses when they decide a render object is a child.
Only for use by subclasses when changing their child lists. Calling this in other cases will lead to an inconsistent tree and probably cause crashes.
Implementation
@override
void adoptChild(RenderBox child) {
super.adoptChild(child);
final SliverVariableSizeBoxAdaptorParentData childParentData =
child.parentData as SliverVariableSizeBoxAdaptorParentData;
if (!childParentData._keptAlive) childManager.didAdoptChild(child);
}