![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  
if (prev == null || next == null) {
      return false;
    }
     W
    if (
      next.hasOwnProperty('baseState') &&
      next.hasOwnProperty('memoizedState') &&
      next.hasOwnProperty('next') &&
      next.hasOwnProperty('queue')
    ) {
      while (next !== null) {
        if (didHookChange(prev, next)) {
          return true;
        } else {
          next = next.next;
          prev = prev.next;
        }
      }
    }
    return false;
  }
  function getChangedHooksIndices(prev: any, next: any): null | Array<number> {
    if (enableProfilerChangedHookIndices) {