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];
```

Object.assign(fakeNativeEvent, nativeEventData);
    if (ReactTestUtils.isDOMComponent(domComponentOrNode)) {
      ReactTestUtils.simulateNativeEventOnDOMComponent(
        eventType,
        domComponentOrNode,
        fakeNativeEvent
      );
    } else if (domComponentOrNode.tagName) {
      
      ReactTestUtils.simulateNativeEventOnNode(
        eventType,
        domComponentOrNode,
        fakeNativeEvent
      );
    }
  };
}
Object.keys(topLevelTypes).forEach(function(eventType) {
  
  var convenienceName = eventType.indexOf('top') === 0 ?
    eventType.charAt(3).toLowerCase() + eventType.substr(4) : eventType;
  /**
   * @param {!Element|ReactDOMComponent} domComponentOrNode
   * @param {?Event} nativeEventData Fake native event to use in SyntheticEvent.
   */
  ReactTestUtils.SimulateNative[convenienceName] =
    makeNativeSimulator(eventType);
});
module.exports = ReactTestUtils;