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.

operations.forEach(operation => {
      var {instanceID} = operation;
      var nextParentID = instanceID;
      while (nextParentID) {
        isDefinitelyNotWastedByID[nextParentID] = true;
        nextParentID = treeSnapshot[nextParentID].parentID;
      }
    });
    
    
    var renderedCompositeIDs = {};
    measurements.forEach(measurement => {
      var {instanceID, timerType} = measurement;
      if (timerType !== 'render') {
        return;
      }
      renderedCompositeIDs[instanceID] = true;
    });
    measurements.forEach(measurement => {
      var {duration, instanceID, timerType} = measurement;
      if (timerType !== 'render') {
        return;
      }
      
      
      var { updateCount } = treeSnapshot[instanceID];
      if (isDefinitelyNotWastedByID[instanceID] || updateCount === 0) {
        return;
      }