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];
```

if (__DEV__) {
    eventHandlers.forEach(function(handler) {
      try {
        if (handler[handlerFunctionName]) {
          handler[handlerFunctionName](arg1, arg2, arg3, arg4, arg5);
        }
      } catch (e) {
        warning(
          handlerDoesThrowForEvent[handlerFunctionName],
          'exception thrown by devtool while handling %s: %s',
          handlerFunctionName,
          e.message
        );
        handlerDoesThrowForEvent[handlerFunctionName] = true;
      }
    });
  }
}
var isProfiling = false;
var flushHistory = [];
var currentFlushNesting = 0;
var currentFlushMeasurements = null;
var currentFlushStartTime = null;
var currentTimerDebugID = null;
var currentTimerStartTime = null;
var currentTimerType = null;
function resetMeasurements() {