delegateFrom method
Delegates all states and context from a given controller to itself and removes all states from the given controller, ensuring that each state exists only once in the controller.
Implementation
delegateFrom(TouchRippleController other) {
_states.clear();
_states.addAll(other._states..clear());
_stateMap.clear();
_stateMap.addAll(other._stateMap..clear());
context = other.context;
}