periment is finished, replace the promise so that we can
  // kick off experiments that depend on the result of this experiment.
  function finish(result) {
    var toSatisfy = canAppearInBody;
    if (toSatisfy instanceof Promise) {
      canAppearInBody = result;
      toSatisfy.satisfy();
    }
    displayJson(result, document.getElementById('nests-in-body-json'))
  }
  if (canAppearInBody instanceof Promise) {
    runExperiment(nestInBody, isNestedInBody, newBlankObject(), finish);
  } else {
    finish