<!DOCTYPE html>
<script src="../../resources/run-after-layout-and-paint.js"></script>
<script>
onload = function() {
  runAfterLayoutAndPaint(function() {
    document.getElementById('iframe').style.width = '150px';
  }, true);
};
</script>
<iframe id="iframe"
    srcdoc="<div style='width:50px; height:50px; background-color:blue; float:right'></div>"
    style="width: 100px; height: 100px">
</iframe>