Chrome Version: 57.0.2987.100
Chrome OS Version: 9202.51.0
Chrome OS Platform: Elm

Steps To Reproduce:
(1) Open a Web App and make it full-screen, for example "Text":
  https://chrome.google.com/webstore/detail/text/mmfbcljfglbokpmkimbfghdkjmjhdgbg
(2) Fill up the page with some garbage text (just to make it more interesting than just plain white)
(3) Open a new Chrome Window, make it full screen and navigate to a youtube playlist, for example: https://www.youtube.com/watch?v=y8ac1Qg-r-8&index=1&list=PLWKXJQUwVcfexiFdxZDrFGCx7RGbsuQUV
(4) As each video loads & starts, press "fast-forward" to start next video

Expected Result:

Between each video in the playlist, the video page is black.

Actual Result:

Sometimes, between videos the background (ie "Text" App page) is shown in the youtube video rectangle.  See attached video @ 0:17-0:18.

How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)

Sometimes.
Actually, I originally noticed this when videos would cut to a youtube video add.  The background window contents would sometimes be displayed during the transition in-to/out-of the ad.

What is the impact to the user, and is there a workaround? If so, what is
it?

Seeing your background content briefly between videos is distracting.
 

Deleted: youtube_playlist_background_shown.webm 2.4 MB

	youtube_playlist_background_shown.webm 2.4 MB View Download