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];
```

}
      return false;
    }
    delete instancesByReactRootID[prevComponent._instance.rootID];
    ReactUpdates.batchedUpdates(
      unmountComponentFromNode,
      prevComponent,
      container,
      false
    );
    return true;
  },
  _mountImageIntoNode: function(
    markup,
    container,
    instance,
    shouldReuseMarkup,
    transaction
  ) {
    invariant(
      container && (
        container.nodeType === ELEMENT_NODE_TYPE ||
        container.nodeType === DOC_NODE_TYPE ||
        container.nodeType === DOCUMENT_FRAGMENT_NODE_TYPE
      ),
      'mountComponentIntoNode(...): Target container is not valid.'
    );
    if (shouldReuseMarkup) {
      var rootElement = getReactRootElementInContainer(container);
      if (ReactMarkupChecksum.canReuseMarkup(markup, rootElement)) {