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__) {
      if (isProfiling && currentFlushNesting > 0) {
        warning(
          currentTimerType === timerType,
          'There is an internal error in the React performance measurement code. ' +
          'We did not expect %s timer to stop while %s timer is still in ' +
          'progress for %s instance. Please report this as a bug in React.',
          timerType,
          currentTimerType || 'no',
          (debugID === currentTimerDebugID) ? 'the same' : 'another'
        );
        currentFlushMeasurements.push({
          timerType,
          instanceID: debugID,
          duration: performanceNow() - currentTimerStartTime,
        });
        currentTimerStartTime = null;
        currentTimerDebugID = null;
        currentTimerType = null;
      }
    }
    emitEvent('onEndLifeCycleTimer', debugID, timerType);
  },
  onBeginReconcilerTimer(debugID, timerType) {