performRebuild method
Cause the widget to update itself.
Called by rebuild after the appropriate checks have been made.
The base implementation only clears the dirty flag.
Implementation
@override
void performRebuild() {
super.performRebuild();
// All widget-refresh work happens lazily in [createChild] during
// layout (see [_dirtyKeys]). If the framework marks us dirty, the
// super call satisfies that contract — the actual reconciliation
// lands when the next layout fires and iterates cache-region keys.
}