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];
```

while (true) {
    var node = startNode.nextSibling;
    if (node === closingComment) {
      
      break;
    } else {
      parentNode.removeChild(node);
    }
  }
}
function replaceDelimitedText(openingComment, closingComment, stringText) {
  var parentNode = openingComment.parentNode;
  var nodeAfterComment = openingComment.nextSibling;
  if (nodeAfterComment === closingComment) {
    
    
    if (stringText) {
      insertChildAt(
        parentNode,
        document.createTextNode(stringText),
        nodeAfterComment
      );
    }