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];
```

'parentComponent must be a valid React Component'
    );
    return ReactMount._renderSubtreeIntoContainer(
      parentComponent,
      nextElement,
      container,
      callback
    );
  },
  _renderSubtreeIntoContainer: function(parentComponent, nextElement, container, callback) {
    ReactUpdateQueue.validateCallback(callback, 'ReactDOM.render');
    invariant(
      ReactElement.isValidElement(nextElement),
      'ReactDOM.render(): Invalid component element.%s',
      (
        typeof nextElement === 'string' ?
          ' Instead of passing a string like \'div\', pass ' +
          'React.createElement(\'div\') or <div />.' :
        typeof nextElement === 'function' ?
          ' Instead of passing a class like Foo, pass ' +
          'React.createElement(Foo) or <Foo />.' :
        
        nextElement != null && nextElement.props !== undefined ?
          ' This may be caused by unintentionally loading two independent ' +
          'copies of React.' :
          ''
      )
    );
    warning(
      !container || !container.tagName ||