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.

var stats = getExclusive(flushHistory);
  var table = stats.map(item => {
    var {key, instanceCount, totalDuration} = item;
    var renderCount = item.counts.render || 0;
    var renderDuration = item.durations.render || 0;
    return {
      'Component': key,
      'Total time (ms)': roundFloat(totalDuration),
      'Instance count': instanceCount,
      'Total render time (ms)': roundFloat(renderDuration),
      'Average render time (ms)': renderCount ?
        roundFloat(renderDuration / renderCount) :
        undefined,
      'Render count': renderCount,
      'Total lifecycle time (ms)': roundFloat(totalDuration - renderDuration),
    };
  });
  console.table(table);
}
function printInclusive(flushHistory) {