Version: ChromeDev @ 50.0.2661.9
OS: Nexus 9 @ 5.1.1

What steps will reproduce the problem?
1. Enable TalkBack
2. Go to youtube.com
3. Start a video
4. Enter fullscreen
5. Keep swiping using linear navigation (in a direction of your choice)

What is the expected output? What do you see instead?
Expected:
Only video and soft key bar are focused using swipes

Actual:
Items in the background (recommended videos etc.) are being read out, even though they are not visible on the screen

Please use labels and text to provide additional information.
Will do.