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 <div><p>Hi.</p></div>;
      }
      var node = document.createElement('div');
      ReactDOM.render(<Foo />, node);
      var inst = ReactDOMComponentTree.getInstanceFromNode(node.firstChild);
      assertHistoryMatches([{
        instanceID: inst._debugID,
        type: 'mount',
        payload: ReactDOMFeatureFlags.useCreateElement ?
          'DIV' :
          '<div data-reactroot="" data-reactid="1">' +
          '<p data-reactid="2">Hi.</p></div>',
      }]);
    });
    it('gets recorded for composite roots that return null', () => {
      function Foo() {