This is a kind of oversight from https://chromestatus.com/feature/6643371200217088, at that time all other ARIA attributes from the IDL (https://w3c.github.io/aria/#idl-interface) were shipped, but this one was missing. This is a small change that will also include the role attribute as one more of the reflection ARIA properties available. This should have shipped in M81 (https://groups.google.com/a/chromium.org/g/blink-dev/c/882iPcdnNQs/m/UP-PI8H2DwAJ) together with the rest of attributes, by for some reason this wasn't done (probably because it was originally developed under a different runtime flag).
Final published standard: Recommendation, Living Standard, Candidate Recommendation, or similar final form
Status in Chromium
Enabled by default
Consensus & Standardization
Last updated on 2022-05-15