Counting when animations end doesn't work properly

[IanLunn]

When binding transitionEnd to an element, sometimes a transitionEnd is triggered more than once for a specific element. This means that on some frames, Sequence thinks the frame has ended animating sooner than it has and the next frame can be initiated.

[IanLunn]

transitionEnd is triggered not just when a transition ends but also in other instances, when a transform scale is completed for example. Originally, I was just counting the number of elements being animated and not allowing the next frame to be initiated until the same number of transitionEnds had occurred.

I've now made it so that the elements being animated are stored in an object with a value of false. Only when a transitionEnd has completed for a specific element will it be given a value of true. When all elements are true, the next frame will then be initiated.