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];
```

instanceID: inst._debugID,
          type: 'remove attribute',
          payload: 'disabled',
        }]);
      });
    });
    describe('custom attribute', () => {
      it('gets recorded during mount', () => {
        var node = document.createElement('div');
        ReactDOM.render(<div data-x="rad" data-y={42} />, node);
        var inst = ReactDOMComponentTree.getInstanceFromNode(node.firstChild);
        if (ReactDOMFeatureFlags.useCreateElement) {
          assertHistoryMatches([{
            instanceID: inst._debugID,
            type: 'update attribute',
            payload: { 'data-x': 'rad' },
          }, {
            instanceID: inst._debugID,
            type: 'update attribute',
            payload: { 'data-y': 42 },
          }, {
            instanceID: inst._debugID,
            type: 'mount',
            payload: 'DIV',
          }]);
        } else {
          assertHistoryMatches([{
            instanceID: inst._debugID,
            type: 'mount',
            payload: '<div data-x="rad" data-y="42" data-reactroot="" ' +