Move Picture-in-Picture actions into the Google Meet page directly

[arnellebalane]

Basically a Chrome update now requires requestPictureInPicture calls to require a user gesture. So we can't call it now from the popup window of the extension. We need to move the buttons that enable Picture-in-Picture directly into the page itself so the user needs to click on it.

The current idea is to add a Picture-in-Picture button in each video in the call, and the user will click on the button for participant that they want to place in a PiP window. We will also phase out the PiP extension popup UI.