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];
```

var key;
    for (key in renderedChildren) {
      if (!renderedChildren.hasOwnProperty(key)) {
        continue;
      }
      ret = ret.concat(
        findAllInRenderedTreeInternal(
          renderedChildren[key],
          test
        )
      );
    }
  } else if (
    ReactElement.isValidElement(currentElement) &&
    typeof currentElement.type === 'function'
  ) {
    ret = ret.concat(
      findAllInRenderedTreeInternal(inst._renderedComponent, test)
    );
  }
  return ret;
}
/**
 * Utilities for making it easy to test React components.
 *
 * See https://facebook.github.io/react/docs/test-utils.html
 *
 * Todo: Support the entire DOM.scry query syntax. For now, these simple
 * utilities will suffice for testing purposes.
 * @lends ReactTestUtils