src/smoothscroll.js
function findScrollableParent(el) {
    while (el !== d.body && isScrollable(el) === false) {
      el = el.parentNode || el.host;
    }

    return el;
  }
function findScrollableParent(el) {
    while (el !== d.body && isScrollable(el) === false) {
      el = el.parentNode || el.host;
    }

    return el;
  }
function findScrollableParent ( el ) { while ( el !== d . body && isScrollable ( el ) === false ) { el = el . parentNode || el . host ; } return el ; }
finds scrollable parent of an element
@method findScrollableParent
@param {Node} el
@returns {Node} el
finds scrollable parent of an element