Youtube iframe not working in some devices.

[QuinsZouls]

Description

In several devices, especially mobile versions, when playing a YouTube video with the iframe, this message appears: "Your browser does not recognize any of the video formats available." in the desktop version works perfectly, but this is not the case with certain devices

Live Demo

https://jsbin.com/voxiyij/edit?html,output

Steps to Reproduce

1. Create my-element
2. Pase a iframe video from youtube
3. Play a video

   Expected Results

   the browser plays the video properly

Actual Results

in mobile appears this message: : "Your browser does not recognize any of the video formats available."

Browsers Affected

• [x] Chrome
• [ ] Firefox
• [x] Edge
• [x] Safari 11
• [x] Safari 10
• [ ] IE 11

Versions

• Polymer: v3.2.0