Windows 8 Metro, supposedly. They designed it to be either vector graphics or for bitmaps you have to supply multiple sizes. The largest size is chosen so that higher resolutions than that won't be neccesary because the human eye can't perceive it, so it will be future proof (at least that's what their marketing says).
FWIW, that's exactly the approach Apple has taken with both iOS and OS X. Some elements are rendered as vector graphics, most are rendered as bitmaps and the app provides a 1x and 2x bitmap.
I've yet to see any platform where this is the case.