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];
```

var minLen = Math.min(string1.length, string2.length);
  for (var i = 0; i < minLen; i++) {
    if (string1.charAt(i) !== string2.charAt(i)) {
      return i;
    }
  }
  return string1.length === string2.length ? -1 : minLen;
}
/**
 * @param {DOMElement|DOMDocument} container DOM element that may contain
 * a React component
 * @return {?*} DOM element that may have the reactRoot ID, or null.
 */
function getReactRootElementInContainer(container) {
  if (!container) {
    return null;
  }
  if (container.nodeType === DOC_NODE_TYPE) {
    return container.documentElement;
  } else {
    return container.firstChild;
  }
}
function internalGetID(node) {