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];
```

var transaction = ReactUpdates.ReactReconcileTransaction.getPooled(true);
  renderer._render(element, transaction, context);
  ReactUpdates.ReactReconcileTransaction.release(transaction);
}
ReactShallowRenderer.prototype.getRenderOutput = function() {
  return (
    (this._instance && this._instance._renderedComponent &&
     this._instance._renderedComponent._renderedOutput)
    || null
  );
};
ReactShallowRenderer.prototype.unmount = function() {
  if (this._instance) {
    this._instance.unmountComponent(false);
  }
};
ReactShallowRenderer.prototype._render = function(element, transaction, context) {
  if (this._instance) {
    this._instance.receiveComponent(element, transaction, context);
  } else {
    var instance = new ShallowComponentWrapper(element);
    instance.mountComponent(transaction, null, null, context);
    this._instance = instance;