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 rootEl = getReactRootElementInContainer(container);
  if (rootEl) {
    var inst = ReactDOMComponentTree.getInstanceFromNode(rootEl);
    return !!(inst && inst._nativeParent);
  }
}
function getNativeRootInstanceInContainer(container) {
  var rootEl = getReactRootElementInContainer(container);
  var prevNativeInstance =
    rootEl && ReactDOMComponentTree.getInstanceFromNode(rootEl);
  return (
    prevNativeInstance && !prevNativeInstance._nativeParent ?
    prevNativeInstance : null
  );
}
function getTopLevelWrapperInContainer(container) {
  var root = getNativeRootInstanceInContainer(container);
  return root ? root._nativeContainerInfo._topLevelWrapper : null;
}
/**
 * Temporary (?) hack so that we can store all top-level pending updates on
 * composites instead of having to worry about different types of components