and watch FPS decrease</button>
<button onclick="stop()">Stop expensive action</button>
<button onclick="display()">Alert FPS</button>
<div id="output"></div>
</body>
<script>

  var fpsDisplay = new goog.debug.FpsDisplay();
  fpsDisplay.render(document.getElementById('fpsdisplay'));

  var handle;
  function doSomethingExpensive() {
    var output = document.getElementById('output');
    var appender = function() {
      output.innerHTML += goog.string.repeat('<div>a </div>', 20);
      // Force layout.
  