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('onBeforeUpdateComponent', debugID, element);
  },
  onUpdateComponent(debugID) {
    checkDebugID(debugID);
    emitEvent('onUpdateComponent', debugID);
  },
  onUnmountComponent(debugID) {
    checkDebugID(debugID);
    emitEvent('onUnmountComponent', debugID);
  },
  onTestEvent() {
    emitEvent('onTestEvent');
  },
};
if (__DEV__) {
  var ReactInvalidSetStateWarningDevTool = require('ReactInvalidSetStateWarningDevTool');
  var ReactHostOperationHistoryDevtool = require('ReactHostOperationHistoryDevtool');
  var ReactComponentTreeDevtool = require('ReactComponentTreeDevtool');
  ReactDebugTool.addDevtool(ReactInvalidSetStateWarningDevTool);
  ReactDebugTool.addDevtool(ReactComponentTreeDevtool);
  ReactDebugTool.addDevtool(ReactHostOperationHistoryDevtool);
  var url = (ExecutionEnvironment.canUseDOM && window.location.href) || '';
  if ((/[?&]react_perf\b/).test(url)) {
    ReactDebugTool.beginProfiling();
  }
}
module.exports = ReactDebugTool;