Calling `ReactDefaultPerf.printWasted()` results in:

```
Uncaught TypeError: Cannot read property 'forEach' of undefined
writes.(anonymous function).forEach @ ReactDefaultPerfAnalysis.js:195
Object.keys.forEach @ ReactDefaultPerfAnalysis.js:192
getUnchangedComponents @ ReactDefaultPerfAnalysis.js:191
getInclusiveSummary @ ReactDefaultPerfAnalysis.js:139
ReactDefaultPerf.getMeasurementsSummaryMap @ ReactDefaultPerf.js:118
ReactDefaultPerf.printWasted @ ReactDefaultPerf.js:133
```

(this is on a page internally at Facebook so I assume it's a fairly recent React version)

ReactDOM.render(<App />, container);
    });
    var summary = ReactDefaultPerf.getWasted(measurements);
    expect(summary.length).toBe(2);
    
    expect(summary[0]['Owner > component']).toBe('<root> > App');
    expect(summary[0]['Wasted time (ms)']).not.toBe(0);
    expect(summary[0]['Instances']).toBe(1);
    expect(summary[1]['Owner > component']).toBe('App > Box');
    expect(summary[1]['Wasted time (ms)']).not.toBe(0);
    expect(summary[1]['Instances']).toBe(2);
    
  });
  it('should count no-op update in child as waste', function() {
    var container = document.createElement('div');
    ReactDOM.render(<App />, container);
    
    
    var measurements = measure(() => {
      ReactDOM.render(<App flipSecond={true} />, container);
    });
    var summary = ReactDefaultPerf.getWasted(measurements);
    expect(summary.length).toBe(1);
    
    expect(summary[0]['Owner > component']).toBe('App > Box');
    expect(summary[0]['Wasted time (ms)']).not.toBe(0);
    expect(summary[0]['Instances']).toBe(1);
    
  });
  function expectNoWaste(fn) {