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                <html lang="en">
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Simple Feature Policy Reporting</title>
  <h1>Feature Policy Reporting Demo</h1>
  <p>A quick and dirty example of how you could watch for Feature Policy violations using a ReportingObserver, and then display them prominently on the page to make them visible.</p>
  <p>To see the Feature Policies in action, you'll need to:</p>
    <li>Be using a Blink-based browser</li>
    <li>Have Experimental Web Platform Features enabled (about:flags)</li>
    <li>Enable a Feature-Policy header (<code>unsized-media</code> and <code>oversized-images</code> should do the trick) somehow (I like <a href="">ModHeader</a>)</li>
  <img src="" alt="">
  <img src="" width="100" alt="">



                body {
  padding-bottom: 0;
  font: 100%/1.4em Helvetica, Arial, sans-serif;
  background: #282828;
  color: #fff;
  padding: 1em;
  border-top: 5px solid #da1e28;
  position: fixed;
  top: 1em;
  right: 1em;
  padding: 1em;
  list-style: none;
#reportingAlerts li+li{
  margin-top: 1em;
#reportingAlerts li:before{
  content: 'x';
  color: #fff;
  background: #da1e28;
  border-radius: 50%;
  padding: .3em .6em;
  line-height: 1em;
  margin-right: .5em;


                let reportingAlerts = document.createElement('ul');

const alertBox = document.getElementById('reportingAlerts');

new ReportingObserver((reports, observer) => {
  let fragment = document.createDocumentFragment();
  Object.keys(reports).forEach(function(item) {
    let li = document.createElement('li');
    li.textContent = reports[item].body.message + ': ' + reports[item].body.featureId;
}, {types: ['feature-policy-violation'], buffered: true}).observe();