If it hasn’t already got buy in then it isn’t a web standard, it’s just a Google proposal. Something isn’t automatically a web standard just because Google thinks it’s a good idea.
Here are Mozilla and WebKit positions on this:
> This proposal attempts to solve multiple problems with a single solution. We (Mozilla) recognize the motivation for solving some of the problems, but believe that this is not the right solution to each problem, or in some case a step in the wrong direction.
— https://github.com/mozilla/standards-positions/issues/1076
— https://github.com/WebKit/standards-positions/issues/630
As far as I can see, nobody outside of Google has committed to implementing this.