Remove the Mixin layer of indirection on ReactMultiChild

[vjeux]

As mentioned in #7581 (comment) we can remove the Mixin layer of indirection as it only exports a Mixin and I find it confusing.

[sebmarkbage]

You'll need to update ReactART in its repo too: https://github.com/reactjs/react-art/blob/master/src/ReactART.js#L96

[gaearon]

What is the plan for ReactART? Now that we moved it here, do we just copy stuff into the separate repo once in a while?

[sophiebits]

The copy here is only for backwards-compat unit tests. The other repo is the source of truth.

[sophiebits]

Also, this is not semver-exempt because it breaks react-art. It should be major.

[sophiebits]

(When you need to change the copy of ReactART in this repo to make tests pass, it's a major change.)

[gaearon]

Oh, okay, sorry.
Isn’t the plan to release ReactART that contains a reconciler copy in the next version, like RN?

[sophiebits]

That's probably a good idea but someone needs to make it happen. :)

[sebmarkbage]

The way it works now, it is integrated with the DOM renderer. It will simply change its dependency to depend on react-dom/lib. When we move it to fiber it'll get its fully own renderer though.