React

• Add a new experimental React.unstable_Profiler component for measuring performance. (bvaughn in #12745)

React DOM

• Add support for the Pointer Events specification. (philipp-spiess in #12507)
• Properly call getDerivedStateFromProps() regardless of the reason for re-rendering. (acdlite in #12600 and #12802)
• Fix a bug that prevented context propagation in some cases. (gaearon in #12708)
• Fix re-rendering of components using forwardRef() on a deeper setState(). (gaearon in #12690)
• Fix some attributes incorrectly getting removed from custom element nodes. (airamrguez in #12702)
• Fix context providers to not bail out on children if there's a legacy context provider above. (gaearon in #12586)
• Add the ability to specify propTypes on a context provider component. (nicolevy in #12658)
• Fix a false positive warning when using react-lifecycles-compat in <StrictMode>. (bvaughn in #12644)
• Warn when the forwardRef() render function has propTypes or defaultProps. (bvaughn in #12644)
• Improve how forwardRef() and context consumers are displayed in the component stack. (sophiebits in #12777)
• Change internal event names. This can break third-party packages that rely on React internals in unsupported ways. (philipp-spiess in #12629)

React Test Renderer

• Fix the getDerivedStateFromProps() support to match the new React DOM behavior. (koba04 in #12676)
• Fix a testInstance.parent crash when the parent is a fragment or another special node. (gaearon in #12813)
• forwardRef() components are now discoverable by the test renderer traversal methods. (gaearon in #12725)
• Shallow renderer now ignores setState() updaters that return null or undefined. (koba04 in #12756)

React ART

• Fix reading context provided from the tree managed by React DOM. (acdlite in #12779)

React Call Return (Experimental)

• This experiment was deleted because it was affecting the bundle size and the API wasn't good enough. It's likely to come back in the future in some other form. (gaearon in #12820)

React Reconciler (Experimental)

• The new host config shape is flat and doesn't use nested objects. (gaearon in #12792)