now, HTMLElement and SVGElement have a "style" attribute per each.
https://cs.chromium.org/chromium/src/third_party/blink/renderer/core/html/html_element.idl?q=html_element&sq=package:chromium&dr&l=59
https://cs.chromium.org/chromium/src/third_party/blink/renderer/core/svg/svg_element.idl?q=svg_element&sq=package:chromium&dr&l=30

https://drafts.csswg.org/cssom/#the-elementcssinlinestyle-interface

but mixin keyword is not supported in blink yet.