Does anybody know whether the Google Chrome / Chromium team and the Mozilla team are squarely behind this standardization effort? What about the Apple Safari team?

There's only one rep from Google in the community group. There don't seem to be any from Apple.

[1990s paranoia mode] this could be another Microsoft effort to embrace and suffocate [/1990s paranoia mode]

I made an extension to appease a slight reddit addiction: "What's new reddit?" https://github.com/mrspeaker/whats-new-reddit/ it highlights updates and auto-refreshes things.

I wrote it for Firefox, and then I wondered what it would take to port it to Chrome. The answer was "nothing really" - it worked out of the box for the main functionality. I had to do a small wrapper over loading settings, but having done a million extensions in the past, I was pretty surprised to see it load straight into a different browser!

> The answer was "nothing really" - it worked out of the box for the main functionality.

Do you mean Chrome supports Promises like Firefox does? Last time I checked, the Chrome APIs were using callbacks for all asynchronous operations.

There is a polyfill written by mozilla devs that port the browser namespace and promise based api calls over to chrome if needed.

https://github.com/mozilla/webextension-polyfill