https://twitter.com/grahamperrin/status/923584097691295745
A frame from the screen recording:
… just one Firefox container, dedicated to testing the new look.
Whenever I want to compare the traditional look to the new, I simply send the traditional page to my ‘mobile’ (new look) container.
To regain the traditional look: de-contain the page.
– there’s Decontain, in the frame. A feature of this extension: