![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  
cleanedInspectedElement.props = cleanForBridge(
      cleanedInspectedElement.props,
      createIsPathAllowed('props', null),
    );
    cleanedInspectedElement.state = cleanForBridge(
      cleanedInspectedElement.state,
      createIsPathAllowed('state', null),
    );
    return {
      id,
      responseID: requestID,
      type: 'full-data',
      value: cleanedInspectedElement,
    };
  }
  function logElementToConsole(id) {
    const result = isMostRecentlyInspectedElementCurrent(id)
      ? mostRecentlyInspectedElement
      : inspectElementRaw(id);
    if (result === null) {
      console.warn(`Could not find Fiber with id "${id}"`);
      return;
    }
    const supportsGroup = typeof console.groupCollapsed === 'function';
    if (supportsGroup) {
      console.groupCollapsed(
        `[Click to expand] %c<${result.displayName || 'Component'} />`,
         -
        'color: var(--dom-tag-name-color); font-weight: normal;',
      );