(Regarding the experimental `React.unstable_Profiler` API and reactjs/rfcs/pull/51.)

PR #13058 changed the behavior of React profiling builds to opt host roots into `ProfileMode` if the React DevTools extension is detected. This was necessary in order to have accurate tree base time measurements for the visual flame graphs.

The Profiler plug-in for DevTools does feature detection to determine if it's enabled by looking at each root and seeing if any of the fibers contain an `actualDuration` attribute,

The problem is that the `actualDuration` attribute will be present on v16.4 fibers, which pre-date PR #13058. As a result, the Profiler UI may enable itself with versions of React that it cannot work correctly with.

Perhaps an easy solution would be to rename one of the `unstable_Profiler`'s fiber attributes prior to the next minor release (e.g. `treeBaseTime` -> `treeBaseDuration`) and change the DevTools Profiler to feature check using this new name instead.
if (enableSuspense) {
        if ((finishedWork.mode & StrictMode) === NoEffect) {
          
          
          
          
          
          finishedWork.updateQueue = emptyObject;
          scheduleWork(finishedWork, Sync);
        } else {
          
          
          const currentTime = requestCurrentTime();
          finishedWork.stateNode = {timedOutAt: currentTime};
        }
      }
      return;
    }
    default: {
      invariant(
        false,
        'This unit of work tag should not have side-effects. This error is ' +
          'likely caused by a bug in React. Please file an issue.',
      );
    }
  }
}
function commitAttachRef(finishedWork: Fiber) {
  const ref = finishedWork.ref;
  if (ref !== null) {