(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.
markSuspendedPriorityLevel(root, expirationTime);
      const suspendedExpirationTime = expirationTime;
      const rootExpirationTime = root.expirationTime;
      onSuspend(
        root,
        rootWorkInProgress,
        suspendedExpirationTime,
        rootExpirationTime,
        -1, 
      );
      return;
    } else if (
      
      
      
      
      !root.didError &&
      !isExpired
    ) {
      root.didError = true;
      const suspendedExpirationTime = (root.nextExpirationTimeToWorkOn = expirationTime);
      const rootExpirationTime = (root.expirationTime = Sync);
      onSuspend(
        root,
        rootWorkInProgress,
        suspendedExpirationTime,
        rootExpirationTime,
        -1, 
      );
      return;