UserAgent: Mozilla/5.0 (X11; Linux x86_64; rv:50.0) Gecko/20100101 /

Example URL:
data:text/html,<script>window.onload=function(){ document.body.innerHTML = "<div>"; document.body.firstChild.attachShadow({mode: "open"}); document.body.firstChild.shadowRoot.innerHTML = "<div onclick='this.webkitRequestFullScreen()'>click me</div>"}</script>

Steps to reproduce the problem:
Load
data:text/html,<script>window.onload=function(){ document.body.innerHTML = "<div>"; document.body.firstChild.attachShadow({mode: "open"}); document.body.firstChild.shadowRoot.innerHTML = "<div onclick='this.webkitRequestFullScreen()'>click me</div>"}</script>

Click the text

Browser enters to fullscreen

What is the expected behavior?
Per spec, fullscreen is supported only for elements in document. Otherwise document.fullscreenElement
(document.webkitFullscreenElement) leaks information about the shadow DOM to the light DOM.

What went wrong?
Chrome is not following the spec.
https://fullscreen.spec.whatwg.org

Does it occur on multiple sites: N/A

Is it a problem with a plugin? N/A 

Did this work before? N/A 

Does this work in other browsers? N/A 

Chrome version: Version 53.0.2785.8 dev (64-bit)  Channel: n/a
OS Version: 
Flash Version: Shockwave Flash 11.2 r202