STR:

1. Set media.videocontrols.picture-in-picture.enabled = true
2. Set media.autoplay.allow-muted = false
3. Make sure that media.autoplay.default = 1 (block autoplay).
4. Play any youtube video and activate Picture in Picture (PiP) through the context menu.

PiP popup window is white with no video.

Browser console shows the following error immediately after activating PiP.

Autoplay is only allowed when approved by the user, the site is activated by the user, or media is muted.
NotAllowedError: The play method is not allowed by the user agent or the platform in the current context, possibly because the user denied permission.

As playing video in the pip mode is requested by user, we should activate the new pip document as well in order to make sure media can play without troubles.

Here is the reviewer's commment on Phabricator,

Thanks for this, but I actually don't think this is going to be needed once bug 1521964 is fixed. Bug 1521964 is going to give us a privileged API to copy frames from one <video> onto another <video>, without the later having to "play" at all.

We will put this patch on hold and to see whether the bug would be fixed after landing bug 1521964.

Hi alwu,

Bug 1521964 has landed, and I don't believe we need to simulate user interaction to get the secondary <video> to play (since we're just copying frames over to its VideoFrameContainer). Can you confirm that we can WORKSFORME this bug?

It works for me, thank you!