I was testing latest refactor of PerfTools.
When using printOperations() often (but not always) I get 

```
Uncaught TypeError: Cannot read property 'displayName' of undefined
```

in getOperations() on the line:

```
var {displayName, ownerID} = treeSnapshot[instanceID];
```

*
   * @param {ReactElement} nextElement Component element to render.
   * @param {DOMElement} container DOM element to render into.
   * @param {?function} callback function triggered on completion
   * @return {ReactComponent} Component instance rendered in `container`.
   */
  render: function(nextElement, container, callback) {
    return ReactMount._renderSubtreeIntoContainer(null, nextElement, container, callback);
  },
  /**
   * Unmounts and destroys the React component rendered in the `container`.
   * See https://facebook.github.io/react/docs/top-level-api.html#reactdom.unmountcomponentatnode
   *
   * @param {DOMElement} container DOM element containing a React component.
   * @return {boolean} True if a component was found in and unmounted from
   *                   `container`
   */
  unmountComponentAtNode: function(container) {
    
    
    
    
    warning(
      ReactCurrentOwner.current == null,
      'unmountComponentAtNode(): Render methods should be a pure function ' +
      'of props and state; triggering nested component updates from render ' +
      'is not allowed. If necessary, trigger nested updates in ' +
      'componentDidUpdate. Check the render method of %s.',
      ReactCurrentOwner.current && ReactCurrentOwner.current.getName() ||
        'ReactCompositeComponent'