Re: [css-device-adaptation] Progress?

My main problem with the device-adaptation spec and the `@viewport` rule is
that it enables external style sheets to impact the viewport dimensions.
That can introduce issues around viewport dimensions based resource loading
(so both <link media> based CSS and `srcset`/`<picture>` based responsive
images).

One way to solve this would be to limit `@viewport` inline styles in the
document's head, and add smarts to the UAs parsing mechanisms so that they
can apply those rules when kicking off loading of viewport-dimensions based
resources.

I also believe that these rules can cause circularity issues. Was that
discussed in the past? Am I correct that they can be declared only on
certain media queries? (either through `@media` or through the `media`
attribute)