Example URL:

Steps to reproduce the problem:
1. Browse any video on www.youtube.com
2. click fullscreen button.
3. When enterFullScreen, click exitFullScreen button.

What is the expected behavior?
The page will exit the fullScreen.

What went wrong?
click exitFullScreen makes no effect.

Did this work before? N/A 

Is it a problem with Flash or HTML5? N/A

Does this work in other browsers? N/A

Chrome version: 53.0.3048.0  Channel: n/a
OS Version: Android O pdk
Flash Version: 

Contents of chrome://gpu: 

From adding log, we found exitFullScreen is called from youtube js as soon as we click enterFullScreen button, which makes fullscreenElementStack empty and result in the latter exitFullScreen request by user.

frame: "0x97401aa8",
 functionName: "",
 lineNumber: 61,
 scriptId: "36",
 url: "https://m.youtube.com/yts/jsbin/cougar-mobile-blazer-nirvana-phone-vflBaKxZy/core.js"}