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];
```

color: 'red',
        backgroundColor: 'yellow',
      }} />, node);
      ReactDOM.render(<div style={{
        color: 'red',
        backgroundColor: 'yellow',
      }} />, node);
      assertHistoryMatches([{
        instanceID: inst._debugID,
        type: 'update styles',
        payload: {
          color: 'red',
          backgroundColor: 'yellow',
        },
      }]);
    });
  });
  describe('update attribute', () => {
    describe('simple attribute', () => {
      it('gets recorded during mount', () => {
        var node = document.createElement('div');
        ReactDOM.render(<div className="rad" tabIndex={42} />, node);
        var inst = ReactDOMComponentTree.getInstanceFromNode(node.firstChild);
        if (ReactDOMFeatureFlags.useCreateElement) {
          assertHistoryMatches([{
            instanceID: inst._debugID,
            type: 'update attribute',
            payload: { className: 'rad' },
          }, {
            instanceID: inst._debugID,