Makes sure that the menu doesn't go off of the screen on either side.
function correctHorizontalAlignment () {
      var dropdown = elements.scrollContainer.getBoundingClientRect(),
          styles   = {};
      if (dropdown.right > root.right - MENU_PADDING) {
        styles.left = (hrect.right - dropdown.width) + 'px';
      }
      elements.$.scrollContainer.css(styles);
    }