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];
```

rootElementSibling = rootElementSibling.nextSibling;
        }
      }
    }
    var shouldReuseMarkup =
      containerHasReactMarkup &&
      !prevComponent &&
      !containerHasNonRootReactChild;
    var component = ReactMount._renderNewRootComponent(
      nextWrappedElement,
      container,
      shouldReuseMarkup,
      parentComponent != null ?
        parentComponent._reactInternalInstance._processChildContext(
          parentComponent._reactInternalInstance._context
        ) :
        emptyObject
    )._renderedComponent.getPublicInstance();
    if (callback) {
      callback.call(component);
    }
    return component;
  },
  /**
   * Renders a React component into the DOM in the supplied `container`.
   * See https://facebook.github.io/react/docs/top-level-api.html#reactdom.render
   *
   * If the React component was previously rendered into `container`, this will
   * perform an update on it and only mutate the DOM as necessary to reflect the
   * latest React component.