function testScrollbarWidth() {
  var width = goog.style.getScrollbarWidth();
  assertTrue(width > 0);

  var outer = goog.dom.getElement('test-scrollbarwidth');
  var inner = goog.dom.getElementsByTagNameAndClass(
      goog.dom.TagName.DIV, null, outer)[0];
  assertTrue('should have a scroll bar', hasVerticalScroll(outer));
  assertTrue('should have a scroll bar', hasHorizontalScroll(outer));

  // Get the inner div absolute width
  goog.style.setStyle(outer, 'width', '100%');
  assertTrue('should have a scroll bar', hasVerticalScroll(outer));
  assertFalse('should not have a scroll bar', hasHorizontalScroll(outer));
  var innerAbsoluteWidth = inner.offsetWidth;

  // Leave the vertical scroll and remove the horizontal by using the scroll
  // bar width calculation.
  goog.style.setStyle(outer, 'width', (innerAbsoluteWidth + width) + 'px');
  assertTrue('should have a scroll bar', hasVerticalScroll(outer));
  assertFalse('should not have a scroll bar', hasHorizontalScroll(outer));

  // verify by adding 1 more pixel (brings back the vertical scroll bar).
  goog.style.setStyle(outer, 'width', (innerAbsoluteWidth + width - 1) + 'px');
  assertTrue('should have a scroll bar', hasVerticalScroll(outer));
  assertTrue('should have a scroll bar', hasHorizontalScroll(outer));
}
Tests the scrollbar width calculation. Assumes that there is an element with
id 'test-scrollbarwidth' in the page.