onMount method
This is called by the Effect class when the controller is attached to that effect. Controllers with children should propagate this to their children.
Implementation
@override
void onMount(Effect parent) {
assert(
parent is MeasurableEffect,
'SpeedEffectController can only be applied to a MeasurableEffect',
);
_parentEffect = parent as MeasurableEffect;
super.onMount(parent);
}