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];
```

isCompositeComponentElementWithType: function(inst, type) {
    var internalInstance = ReactInstanceMap.get(inst);
    var constructor = internalInstance
      ._currentElement
      .type;
    return !!(ReactTestUtils.isCompositeComponentElement(inst) &&
             (constructor === type));
  },
  getRenderedChildOfCompositeComponent: function(inst) {
    if (!ReactTestUtils.isCompositeComponent(inst)) {
      return null;
    }
    var internalInstance = ReactInstanceMap.get(inst);
    return internalInstance._renderedComponent.getPublicInstance();
  },
  findAllInRenderedTree: function(inst, test) {
    if (!inst) {
      return [];
    }
    invariant(
      ReactTestUtils.isCompositeComponent(inst),
      'findAllInRenderedTree(...): instance must be a composite component'
    );
    return findAllInRenderedTreeInternal(ReactInstanceMap.get(inst), test);
  },
  /**
   * Finds all instance of components in the rendered tree that are DOM
   * components with the class name matching `className`.
   * @return {array} an array of all the matches.
   */