Failing test: componentWillUnmount called twice

[gaearon]

Adds two tests for #24280. One passes (useLayoutEffect), one that fails (componentWillIUnmount).

The cause is that we clear .destroy fields so they don't get called twice. But we don't have a similar mechanism for classes.

I don't know how to fix this yet.

[sizebot]

Comparing: af73043...36a1726

Critical size changes

Includes critical production bundles, as well as any change greater than 2%:

Name	+/-	Base	Current	+/- gzip	Base gzip	Current gzip
oss-stable/react-dom/cjs/react-dom.production.min.js	=	131.40 kB	131.40 kB	=	41.99 kB	41.99 kB
oss-experimental/react-dom/cjs/react-dom.production.min.js	=	136.45 kB	136.45 kB	=	43.43 kB	43.43 kB
facebook-www/ReactDOM-prod.classic.js	=	433.07 kB	433.07 kB	=	79.60 kB	79.60 kB
facebook-www/ReactDOM-prod.modern.js	=	418.07 kB	418.07 kB	=	77.24 kB	77.24 kB
facebook-www/ReactDOMForked-prod.classic.js	=	433.07 kB	433.07 kB	=	79.61 kB	79.61 kB

Significant size changes

Includes any change greater than 0.2%:

(No significant changes)

Generated by 🚫 dangerJS against 36a1726

[gaearon]

Fixed in #24308.