Apply animation effects as soon as an animation is played

This change forces animation effects to apply themselves within the same script context that attached them to the document timeline.

Illustration:
// getComputedStyle(element).color === 'black';
element.animate([{color: 'green'}, {color: 'white'}], 1);
// getComputedStyle(element).color === 'green';

This simplifies some of the logic used when calling exitModifyCurrentAnimationState(). In almost all circumstances the player has undergone a tick before any animation state modification occurs.