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 this;
  },
  /**
   * Simulates a top level event being dispatched from a raw event that occurred
   * on an `Element` node.
   * @param {Object} topLevelType A type from `EventConstants.topLevelTypes`
   * @param {!Element} node The dom to simulate an event occurring on.
   * @param {?Event} fakeNativeEvent Fake native event to use in SyntheticEvent.
   */
  simulateNativeEventOnNode: function(topLevelType, node, fakeNativeEvent) {
    fakeNativeEvent.target = node;
    ReactBrowserEventEmitter.ReactEventListener.dispatchEvent(
      topLevelType,
      fakeNativeEvent
    );
  },
  /**
   * Simulates a top level event being dispatched from a raw event that occurred
   * on the `ReactDOMComponent` `comp`.
   * @param {Object} topLevelType A type from `EventConstants.topLevelTypes`.
   * @param {!ReactDOMComponent} comp
   * @param {?Event} fakeNativeEvent Fake native event to use in SyntheticEvent.
   */
  simulateNativeEventOnDOMComponent: function(
      topLevelType,
      comp,
      fakeNativeEvent) {
    ReactTestUtils.simulateNativeEventOnNode(
      topLevelType,