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];
```

if (all.length !== 1) {
      throw new Error(
        'Did not find exactly one match (found: ' + all.length + ') ' +
        'for tag:' + tagName
      );
    }
    return all[0];
  },
  /**
   * Finds all instances of components with type equal to `componentType`.
   * @return {array} an array of all the matches.
   */
  scryRenderedComponentsWithType: function(root, componentType) {
    return ReactTestUtils.findAllInRenderedTree(root, function(inst) {
      return ReactTestUtils.isCompositeComponentWithType(
        inst,
        componentType
      );
    });
  },
  /**
   * Same as `scryRenderedComponentsWithType` but expects there to be one result
   * and returns that one result, or throws exception if there is any other
   * number of matches besides one.
   * @return {!ReactComponent} The one match.
   */
  findRenderedComponentWithType: function(root, componentType) {
    var all = ReactTestUtils.scryRenderedComponentsWithType(
      root,
      componentType