|  | <!DOCTYPE html> | 
|  | <html> | 
|  | <head> | 
|  | <title>The green box should not disappear</title> | 
|  | <style> | 
|  | .box { | 
|  | width: 400px; | 
|  | background-color: green; | 
|  | height: 0px; | 
|  | opacity: 0.8; | 
|  | transition: opacity 0.1s; | 
|  | } | 
|  |  | 
|  | body.changed .box { | 
|  | opacity: 1; | 
|  | } | 
|  |  | 
|  | .content { | 
|  | height: 200px; | 
|  | width: 200px; | 
|  | background-color: green; | 
|  | } | 
|  | </style> | 
|  | <script> | 
|  | if (window.testRunner) | 
|  | testRunner.waitUntilDone(); | 
|  |  | 
|  | window.addEventListener('load', () => { | 
|  |  | 
|  | let box = document.getElementsByClassName('box')[0]; | 
|  | box.addEventListener('transitionend', () => { | 
|  | if (window.testRunner) | 
|  | testRunner.notifyDone(); | 
|  | }, false); | 
|  | setTimeout(() => { | 
|  | document.body.classList.add('changed'); | 
|  | }, 0); | 
|  | }, false); | 
|  | </script> | 
|  | </head> | 
|  | <body> | 
|  | <div class="box"> | 
|  | <div class="content"></div> | 
|  | </div> | 
|  | </body> | 
|  | </html> |