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];
```

ReactReconciler.unmountComponent(instance, safely);
  if (container.nodeType === DOC_NODE_TYPE) {
    container = container.documentElement;
  }
  
  while (container.lastChild) {
    container.removeChild(container.lastChild);
  }
}
/**
 * True if the supplied DOM node has a direct React-rendered child that is
 * not a React root element. Useful for warning in `render`,
 * `unmountComponentAtNode`, etc.
 *
 * @param {?DOMElement} node The candidate DOM node.
 * @return {boolean} True if the DOM element contains a direct child that was
 * rendered by React but is not a root element.
 * @internal
 */
function hasNonRootReactChild(container) {