<!DOCTYPE html>
<html>
<body>
<div id="console">Waiting...</div>
<button id="btn1">Step 1</button>
<script id="isolatedScript" type="isolated/world">
document.body.world = 'Isolated';
var bt = document.getElementById('btn1');
bt.addEventListener('click', function() {
  document.getElementById('console').innerHTML = document.body.world;
}, false);
bt.click();
</script>
<script>
document.body.world = 'Main';
if (window.testRunner) {
  testRunner.dumpAsText();
  testRunner.evaluateScriptInIsolatedWorld(1, document.getElementById('isolatedScript').innerHTML);
}
</script>
</body>
</html>