third_party/WebKit/LayoutTests/custom-elements/imports/resources/upgrade.html - chromium/src - Git at Google

 <!DOCTYPE html>
 <x-x id="aa"></x-x>
 <y-y id="bb"></y-y>
 <script>
 'use strict';

 customElements.define('x-x', class extends HTMLElement {
   constructor() {
     super();
     reactions.push({ type: 'constructor', element: this });
   }
 });
 </script>
	<!DOCTYPE html>
	<x-x id="aa"></x-x>
	<y-y id="bb"></y-y>
	<script>
	'use strict';

	customElements.define('x-x', class extends HTMLElement {
	constructor() {
	super();
	reactions.push({ type: 'constructor', element: this });
	}
	});
	</script>