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];
```

shouldReuseMarkup,
      context
    );
    var wrapperID = componentInstance._instance.rootID;
    instancesByReactRootID[wrapperID] = componentInstance;
    if (__DEV__) {
      
      ReactInstrumentation.debugTool.onMountRootComponent(
        componentInstance._renderedComponent._debugID
      );
      ReactInstrumentation.debugTool.onEndFlush();
    }
    return componentInstance;
  },
  /**
   * Renders a React component into the DOM in the supplied `container`.
   *
   * If the React component was previously rendered into `container`, this will
   * perform an update on it and only mutate the DOM as necessary to reflect the
   * latest React component.
   *
   * @param {ReactComponent} parentComponent The conceptual parent of this render tree.
   * @param {ReactElement} nextElement Component element to render.
   * @param {DOMElement} container DOM element to render into.
   * @param {?function} callback function triggered on completion
   * @return {ReactComponent} Component instance rendered in `container`.
   */
  renderSubtreeIntoContainer: function(parentComponent, nextElement, container, callback) {
    invariant(
      parentComponent != null && parentComponent._reactInternalInstance != null,