Need to document that users need to bookmark the ROV site to keep video from getting lost

[BrianAdams]

https://developers.google.com/web/updates/2016/06/persistent-storage?hl=en

Basically Chrome today will delete the video and telemetry data saved from dives if the computer is running short on drive space ... unless the site is in the users bookmarks. If the site is in the users bookmarks the data will never be automatically deleted.

This is a temporary requirement until the Chrome team roles out the final APIs for asking the user explicitly for permission to save the data forever in the browser.