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];
```

DOMLazyTree.insertTreeBefore(parentNode, childTree, referenceNode);
}
function moveChild(parentNode, childNode, referenceNode) {
  if (Array.isArray(childNode)) {
    moveDelimitedText(parentNode, childNode[0], childNode[1], referenceNode);
  } else {
    insertChildAt(parentNode, childNode, referenceNode);
  }
}
function removeChild(parentNode, childNode) {