Currently window.outerHeight basically matches window.innerHeight. On desktop, the meaning of outerHeight/outerWidth is to return the window size "including window chrome" (https://developer.mozilla.org/en-US/docs/Web/API/Window/outerWidth).

Using this interpretation on mobile would mean that outerHeight would include the URL bar height. This would make it more useful and allow working in the same space as `vh` units currently do (as mentioned: https://twitter.com/appsforartists/status/935683728801538048)

This could have interop and (more likely) web compat impact so it's something that we'd have to investigate.