$.fn.animationComplete doesn't release callback when $.support.cssTransitions=true

[nonplus]

In v1.2.0 and earlier, $.fn.animationComplete(callback) leaks the supplied callback.

When $.support.cssTransitions is true in $.fn.animationComplete(), the function attaches the callback to both the webkitAnimationEnd and the animationend events.

However, only one of these will fire depending on the browser. For example, on WebkKit, the webkitAnimationEnd will fire but the callback will be retained on behalf of the animationend event which never fires. This leads to memory leaks.

The fix is to attach to a browser-specific event:

//animation complete callback
var animationEndEvent = "WebKitTransitionEvent" in window ? "webkitAnimationEnd" : "animationend";
$.fn.animationComplete = function(callback) {
    if ($.support.cssTransitions) {
        return $(this).one(animationEndEvent, callback);
    } else {
        // defer execution for consistency between webkit/non webkit
        setTimeout(callback, 0);
        return $(this);
    }
};