event bubbling: beginEvent
For the event beginEvent bubbling is not applicable.
The beginEvent of the stroke animation of the circle
starts the animation for cx directly. If bubbling would
be applicable, cy would start too, but without bubbling
the cy animation does not start at all.
The cx animations is repeated once.
The circle moves always along the grey line.
If the red fill of the circle gets visible, an error is occured.