I've tested the new Perf tools on one of the screens in one app I'm working on and it works great :)

One thing I wanted also on the old one Perf tools was to be able to check whether the Perf tools are started or stopped, so basically exposing `ReactDebugTool`'s `isProfiling` variable. My use for that is that I have a keyboard shortcut (in development) bound to start/stop the Perf tools and currently I'm forced to maintain such a variable myself to know whether to start or stop (which gets out of sync if I start/stop the perf tools without the keyboard shortcut).

If you don't think it's worthwhile to expose `isProfiling` feel free to close this issue.

durations: { ctor: 3, render: 4 },
      totalDuration: 7,
    }]);
  });
  it('warns once when using getMeasurementsSummaryMap', function() {
    var measurements = measure(() => {});
    spyOn(console, 'error');
    ReactPerf.getMeasurementsSummaryMap(measurements);
    expect(console.error.calls.length).toBe(1);
    expect(console.error.argsForCall[0][0]).toContain(
      '`ReactPerf.getMeasurementsSummaryMap(...)` is deprecated. Use ' +
      '`ReactPerf.getWasted(...)` instead.'
    );
    ReactPerf.getMeasurementsSummaryMap(measurements);
    expect(console.error.calls.length).toBe(1);
  });
  it('warns once when using printDOM', function() {
    var measurements = measure(() => {});
    spyOn(console, 'error');
    ReactPerf.printDOM(measurements);
    expect(console.error.calls.length).toBe(1);
    expect(console.error.argsForCall[0][0]).toContain(
      '`ReactPerf.printDOM(...)` is deprecated. Use ' +
      '`ReactPerf.printOperations(...)` instead.'
    );
    ReactPerf.printDOM(measurements);
    expect(console.error.calls.length).toBe(1);
  });
});