We always track the last committed Fiber on `FiberInstance.data`.
dcae56f8b7/packages/react-devtools-shared/src/backend/fiber/renderer.js (L3068)
So we can now remove this complex slow path to get the current fiber.
This directory contains code shared between several DevTools packages:
- /packages/react-devtools-core
- /packages/react-devtools-extensions
- /packages/react-devtools-inline
It is not published or released anywhere directly.