![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 (a.alternate !== b) {
        throw Error(
          "Return fibers should always be each others' alternates. " +
            'This error is likely caused by a bug in React. Please file an issue.',
        );
      }
    }
     I
     u
    if (a.tag !== HostRoot) {
      throw Error('Unable to find node on an unmounted component.');
    }
    if (a.stateNode.current === a) {
       W
      return fiber;
    }
     Otherwise B has to be current branch.
    return alternate;
  }
   E
  function prepareViewAttributeSource(
    id: number,
    path: Array<string | number>,
  ): void {
    if (isMostRecentlyInspectedElement(id)) {
      window.$attribute = getInObject(
        ((mostRecentlyInspectedElement: any): InspectedElement),
        path,