Gets the transferable delegate for the given id.
function _getTransferable(item, view, id) {
        // 1. If view supports getTransferable, use that
        if (view.getTransferable) {
            return view.getTransferable(id);
        }
        // 2. If view is derived from layoutcontroller, use that
        if (view.getSpec && view.get && view.replace) {
            if (view.get(id) !== undefined) {
                return {
                    get: function() {
                        return view.get(id);
                    },
                    show: function(renderable) {
                        view.replace(id, renderable);
                    },
                    getSpec: _getViewSpec.bind(this, item, view, id)
                };
            }
        }
        // 3. If view has an embedded layout, use that as fallback
        if (view.layout) {
            return _getTransferable.call(this, item, view.layout, id);
        }
    }