content/test/data/browser_plugin_embedder.html

<script type="text/javascript">
function SetSrc(src) {
  var plugin = document.getElementById('plugin');
  plugin.src = src;
}
function SetSize(w, h) {
  var plugin = document.getElementById('plugin');
  plugin.width = w;
  plugin.height = h;
}
function PostMessage(data, shouldTargetIframe) {
  plugin = document.getElementById('plugin');
  // TODO(fsamuel): contentWindow can be accessed directly once
  // http://wkbug.com/85679 lands.
  if (shouldTargetIframe) {
    plugin.contentWindow.frames[0].postMessage('testing123', '*');
  } else {
    plugin.contentWindow.frames.postMessage('testing123', '*');
  }
}
function SetTitle(str) {
  document.title = str;
}
document.title = 'embedder';
</script>

<object id="plugin"
    tabindex="0"
    type="application/browser-plugin"
    width="640"
    height="480"
    border="0px"></object>
<script type="text/javascript">
var msg;
function receiveMessage(event) {
  msg = event.data;
  if (msg == 'ready') {
    document.title = 'ready';
    return;
  }
  if (msg.indexOf('stop_ack') == -1) {
    event.source.postMessage('stop', '*');
  } else {
    var name = msg.replace("stop_ack", "").trim();
    if (name !== '') {
      window.document.title = name;
    } else {
      window.document.title = 'main guest';
    }
  }
}

var plugin = document.getElementById('plugin');
window.addEventListener('message', receiveMessage, false);
plugin.addEventListener('-internal-instanceid-allocated', function(e) {
  var detail = e.detail ? JSON.parse(e.detail) : {};
  plugin['-internal-attach'](detail.windowId, {});
});
</script>