bug

Warning displayed in console about internal error of React performance measurement code.

``` js
import React from 'react';
import { render } from 'react-dom';
import Perf from 'react-addons-perf';
import { browserHistory, Router } from 'react-router';

import routes from './routes';
import persist from 'altFlux/persist';

persist('docs');

const target = document.getElementById('app');

Perf.start();

render(
  <Router
    routes={routes}
    history={browserHistory}
  />,
  target,
  () => {
    Perf.stop();
    Perf.printWasted();
  }
);
```

![screen shot 2016-05-23 at 9 21 08 am](https://cloud.githubusercontent.com/assets/91464/15472297/5e440d48-20c8-11e6-99d7-363f6d1bdcce.png)

15.1.0
Google Chrome

checkDebugID(debugID);
    emitEvent('onBeginReconcilerTimer', debugID, timerType);
  },
  onEndReconcilerTimer(debugID, timerType) {
    checkDebugID(debugID);
    emitEvent('onEndReconcilerTimer', debugID, timerType);
  },
  onBeginProcessingChildContext() {
    emitEvent('onBeginProcessingChildContext');
  },
  onEndProcessingChildContext() {
    emitEvent('onEndProcessingChildContext');
  },
  onHostOperation(debugID, type, payload) {
    checkDebugID(debugID);
    emitEvent('onHostOperation', debugID, type, payload);
  },
  onSetState() {
    emitEvent('onSetState');
  },
  onSetDisplayName(debugID, displayName) {
    checkDebugID(debugID);
    emitEvent('onSetDisplayName', debugID, displayName);
  },
  onSetChildren(debugID, childDebugIDs) {