assignOwner method
Set the owner of the element. The owner will be propagated to all the descendants of this element.
The owner manages the dirty elements list.
The WidgetsBinding introduces the primary owner, WidgetsBinding.buildOwner, and assigns it to the widget tree in the call to runApp. The binding is responsible for driving the build pipeline by calling the build owner's BuildOwner.buildScope method. See WidgetsBinding.drawFrame.
Implementation
void assignOwner(BuildOwner owner) {
_owner = owner;
}