(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.
break;
    case HostPortal:
      parent = parentFiber.stateNode.containerInfo;
      isContainer = true;
      break;
    default:
      invariant(
        false,
        'Invalid host parent fiber. This error is likely caused by a bug ' +
          'in React. Please file an issue.',
      );
  }
  if (parentFiber.effectTag & ContentReset) {
    
    resetTextContent(parent);
    
    parentFiber.effectTag &= ~ContentReset;
  }
  const before = getHostSibling(finishedWork);
  
  
  let node: Fiber = finishedWork;
  while (true) {
    if (node.tag === HostComponent || node.tag === HostText) {
      if (before) {
        if (isContainer) {
          insertInContainerBefore(parent, node.stateNode, before);
        } else {
          insertBefore(parent, node.stateNode, before);
        }