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];
```

/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule ReactTestUtils
 */
'use strict';
var EventConstants = require('EventConstants');
var EventPluginHub = require('EventPluginHub');
var EventPluginRegistry = require('EventPluginRegistry');
var EventPropagators = require('EventPropagators');
var React = require('React');
var ReactDefaultInjection = require('ReactDefaultInjection');
var ReactDOM = require('ReactDOM');
var ReactDOMComponentTree = require('ReactDOMComponentTree');
var ReactElement = require('ReactElement');
var ReactBrowserEventEmitter = require('ReactBrowserEventEmitter');
var ReactCompositeComponent = require('ReactCompositeComponent');
var ReactInstanceMap = require('ReactInstanceMap');
var ReactUpdates = require('ReactUpdates');
var SyntheticEvent = require('SyntheticEvent');
var emptyObject = require('emptyObject');
var findDOMNode = require('findDOMNode');
var invariant = require('invariant');
var topLevelTypes = EventConstants.topLevelTypes;
function Event(suffix) {}