Many thanks to everybody who has responded and for a lively and a productive discussion!
Quick clarification: the proposal is to include *device* capabilities in the HTTP headers, so when we say "screen width and height" we mean device screen width and height which is constant (but can have multiple values: for portrait and landscape). There's no proposal or even need to capture user resizing a window and consequent change in viewport size. That is a completely different discussion. Thank you Irakli
