pt>
test(function() {
  const sheet = new CSSStyleSheet();
  sheet.replaceSync('span {background-color:green;}');
  assert_equals(document.adoptedStyleSheets.length,0);
  document.adoptedStyleSheets = document.adoptedStyleSheets.concat([sheet]);
  assert_equals(document.adoptedStyleSheets.length,1);

  const host = document.getElementById('host');
  const shadow = host.attachShadow({mode: 'open'});
  shadow.innerHTML = '<span>This should be green</span>';
  assert_equals(shadow.adoptedStyleSheets.length,0);