React

• Add Fragment as named export to React. (@clemmy in #10783)
• Support experimental Call/Return types in React.Children utilities. (@MatteoVH in #11422)

React DOM

• Fix radio buttons not getting checked when using multiple lists of radios. (@landvibe in #11227)
• Fix radio buttons not receiving the onChange event in some cases. (@jquense in #11028)

React Test Renderer

• Fix setState() callback firing too early when called from componentWillMount. (@accordeiro in #11507)

React Reconciler

• Expose react-reconciler/reflection with utilities useful to custom renderers. (@rivenhk in #11683)

Internal Changes

• Many tests were rewritten against the public API. Big thanks to everyone who contributed!