Add mitigating action to window size warning

Tor Browser will now warn users when they change the window size. That's great. But the associated button just says “Ok”. I believe it would be better to provide more active buttons that just one that will dismiss the warning.

How about:

• Unmaximize (when maximized) (or is it too jargony?)
• Restore common window size (change to the next rounded dimension)
• I don’t mind sites learning the size of my screen