![Screenshot 2019-12-16 10 51 05](https://user-images.githubusercontent.com/793565/70934095-fd91ed80-1ff1-11ea-93b5-746e816585ec.png)
There's seems to be circumstances where unmounted DOM/Fibers are kept alive by React DevTools. They're kept alive in `primaryFibers`:
https://github.com/facebook/react/blob/34527063083195558f98108cde10b5d6ad0d6865/packages/react-devtools-shared/src/backend/renderer.js#L772

It seems like a WeakSet would be appropriate and would remove the leak. Otherwise we'd need to understand why recordUnmount isn't called.

CC @bvaughn  
fiber,
          (renderer.currentDispatcherRef: any),
          true,  I
        );
      } finally {
         R
        for (const method in originalConsoleMethods) {
          try {
             $
            console[method] = originalConsoleMethods[method];
          } catch (error) {}
        }
      }
    }
    let rootType = null;
    let current = fiber;
    while (current.return !== null) {
      current = current.return;
    }
    const fiberRoot = current.stateNode;
    if (fiberRoot != null && fiberRoot._debugRootType !== null) {
      rootType = fiberRoot._debugRootType;
    }
    const errors = fiberIDToErrorsMap.get(id) || new Map();
    const warnings = fiberIDToWarningsMap.get(id) || new Map();
    const isErrored =
      (fiber.flags & DidCapture) !== NoFlags ||
      forceErrorForFiberIDs.get(id) === true;
    let targetErrorBoundaryID;
    if (isErrorBoundary(fiber)) {