ViewStack: problems when showing a node immediately after hiding it

[wkeese]

After upgrading to Intern 3 and running the ViewStack unit tests, I get failures in Chrome 48/mac and also other browsers. The first failure is in the Show (reverse, flip) test.

The problem happens when you show a node immediately after hiding it.

ViewStack is supposed to add classes to a node as the transition starts, and then remove the classes when the transition ends 300ms later. The failure is because ViewStack tries to remove the classes before it adds them. It occurs because of two issues:

• When showing a node immediately after hiding it, the transitionEnd event occurs immediately, rather than in 300ms like it's supposed to. Browser bug? I'm not sure. It occurs on multiple browsers.
• I don't know why, but ViewStack has a delay before it adds the classes to nodes that are in transition:

this.defer(function () {
    if (target) {
        $(target).addClass("-d-view-stack-transition");
    }
    if (origin) {
        $(origin).addClass("-d-view-stack-transition -d-view-stack-out");
    }
    if (reverse) {
        setReverse(origin);
        setReverse(target);
    }
    if (target) {
        $(target).addClass("-d-view-stack-in");
    }
}, this._timing);

On Chrome this._timing is 20ms.