function indexOfListener(listeners, listener) {
        var i = listeners.length;
        while (i--) {
            if (listeners[i].listener === listener) {
                return i;
            }
        }

        return -1;
    }
Finds the index of the listener for the event in its storage array.

@param {Function[]} listeners Array of listeners to search through.
@param {Function} listener Method to look for.
@return {Number} Index of the specified listener, -1 if not found
@api private