![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  
overridePropsRenamePath,
    scheduleRefresh,
    setErrorHandler,
    setSuspenseHandler,
    scheduleUpdate,
  } = renderer;
  const supportsTogglingError =
    typeof setErrorHandler === 'function' &&
    typeof scheduleUpdate === 'function';
  const supportsTogglingSuspense =
    typeof setSuspenseHandler === 'function' &&
    typeof scheduleUpdate === 'function';
  if (typeof scheduleRefresh === 'function') {
    
    
    
    
    
    
    renderer.scheduleRefresh = (...args) => {
      try {
        hook.emit('fastRefreshScheduled');
      } finally {
        return scheduleRefresh(...args);
      }
    };
  }