Sample Screencast
Channel: Neil Patel
Date: 29/07/2015

Device - Amazon Fire Phone
OS - Android 4.4.4
ROM - CyanogenMod 11

*A sample screencast using Mirror Beta to check out full screen video playback in portrait on the YouTube app. I have tested this on the Android app.

*To clarify, tapping multiple times on the Build Number enables Developer Mode and tapping on the Android version takes you to the easter egg for your Android version.

Blog Post - http://goo.gl/DO1F99 or http://goo.gl/PoapPB