Changed event handler properties to use lists of callbacks
Changed event handler properties to use lists of callbacks

web-animations/web-animations-js-legacy,birtles/web-animations-js,birtles/web-animations-js,beni55/web-animations-js-legacy,web-animations/web-animations-js-legacy,birtles/web-animations-js,web-animations/web-animations-js-legacy,beni55/web-animations-js-legacy,beni55/web-animations-js-legacy,beni55/web-animations-js-legacy