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];
```

}
    currentFlushStartTime = performanceNow();
    currentFlushMeasurements = [];
    ReactComponentTreeDevtool.purgeUnmountedComponents();
    ReactNativeOperationHistoryDevtool.clearHistory();
  }
}
var ReactDebugTool = {
  addDevtool(devtool) {
    eventHandlers.push(devtool);
  },
  removeDevtool(devtool) {
    for (var i = 0; i < eventHandlers.length; i++) {
      if (eventHandlers[i] === devtool) {
        eventHandlers.splice(i, 1);
        i--;
      }
    }
  },
  beginProfiling() {
    if (__DEV__) {
      if (isProfiling) {
        return;
      }
      isProfiling = true;
      flushHistory.length = 0;
      resetMeasurements();
    }
  },
  endProfiling() {