(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.
return nextProps.shouldComponentUpdate;
      }
      render() {
        
        advanceTimeBy(this.props.byAmount);
        return this.props.children || null;
      }
    };
  });
  it('should auto-Profile all fibers if the DevTools hook is detected', () => {
    const App = ({multiplier}) => {
      advanceTimeBy(2);
      return (
        <React.unstable_Profiler id="Profiler" onRender={onRender}>
          <AdvanceTime byAmount={3 * multiplier} shouldComponentUpdate={true} />
          <AdvanceTime
            byAmount={7 * multiplier}
            shouldComponentUpdate={false}
          />
        </React.unstable_Profiler>