![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  
return false;
      }
      for (let i = 0; i < path.length; i++) {
        current = current[path[i]];
        if (!current) {
          return false;
        }
      }
      return true;
    };
  }
  function updateSelectedElement(inspectedElement: InspectedElement): void {
    const {hooks, id, props} = inspectedElement;
    const fiber = idToArbitraryFiberMap.get(id);
    if (fiber == null) {
      console.warn(`Could not find Fiber with id "${id}"`);
      return;
    }
    const {elementType, stateNode, tag, type} = fiber;
    switch (tag) {
      case ClassComponent:
      case IncompleteClassComponent:
      case IndeterminateComponent:
        global.$r = stateNode;
        break;
      case FunctionComponent:
        global.$r = {
          hooks,
          props,
          type,