(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 (enableProfilerTimer) {
    if (__DEV__) {
      if (nextRoot === null) {
        
        
        
        checkActualRenderTimeStackEmpty();
      }
    }
  }
  isCommitting = false;
  isWorking = false;
  stopCommitLifeCyclesTimer();
  stopCommitTimer();
  if (typeof onCommitRoot === 'function') {
    onCommitRoot(finishedWork.stateNode);
  }
  if (__DEV__ && ReactFiberInstrumentation.debugTool) {
    ReactFiberInstrumentation.debugTool.onCommitWork(finishedWork);
  }
  const expirationTime = root.expirationTime;
  if (expirationTime === NoWork) {
    
    
    legacyErrorBoundariesThatAlreadyFailed = null;
  }
  onCommit(root, expirationTime);
}
function resetExpirationTime(