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];
```

describe('move child', () => {
    it('gets reported when a child is inserted', () => {
      var node = document.createElement('div');
      ReactDOM.render(<div><span key="a" /><p key="b" /></div>, node);
      var inst = ReactDOMComponentTree.getInstanceFromNode(node.firstChild);
      ReactNativeOperationHistoryDevtool.clearHistory();
      ReactDOM.render(<div><p key="b" /><span key="a" /></div>, node);
      assertHistoryMatches([{
        instanceID: inst._debugID,
        type: 'move child',
        payload: {fromIndex: 0, toIndex: 1},
      }]);
    });
  });
  describe('remove child', () => {
    it('gets reported when a child is removed', () => {
      var node = document.createElement('div');
      ReactDOM.render(<div><span key="a" /><p key="b" /></div>, node);
      var inst = ReactDOMComponentTree.getInstanceFromNode(node.firstChild);
      ReactNativeOperationHistoryDevtool.clearHistory();
      ReactDOM.render(<div><span key="a" /></div>, node);
      assertHistoryMatches([{
        instanceID: inst._debugID,
        type: 'remove child',
        payload: {fromIndex: 1},
      }]);
    });
  });
});