Hi, per discussion in:
There's enough usage of -webkit-image-set on the wild that it might be
worth supporting this as an alias of the new syntax (which is a
super-set of what Chrome and WebKit implement with the prefixed syntax)
to improve the experience of Firefox users in HiDPI displays.
WebKit in fact already does this to some extent (they parse
-webkit-image-set(), but serialize it as image-set()).
Standard: CSS resolution in https://github.com/w3c/csswg-drafts/issues/6285
Platform coverage: All
DevTools bug: N/A
Other browsers: Both WebKit and Blink ship this as you could imagine.
WebKit does implement the unprefixed version of the function as
web-platform-tests: Added as part of my Gecko patch.
Let me know if there's any concern with this.