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 null;
      }
      var node = document.createElement('div');
      ReactDOM.render(<Foo />, node);
      var inst = ReactDOMComponentTree.getInstanceFromNode(node.firstChild);
      assertHistoryMatches([{
        instanceID: inst._debugID,
        type: 'mount',
        payload: ReactDOMFeatureFlags.useCreateElement ?
          '#comment' :
          '<!-- react-empty: 1 -->',
      }]);
    });
  });
  describe('update styles', () => {
    it('gets recorded during mount', () => {
      var node = document.createElement('div');
      ReactDOM.render(<div style={{
        color: 'red',
        backgroundColor: 'yellow',