Hi, long time user, first time issuer.

I think I found a bug with the Profiler component. When I click on the `Save profile...` button at the top nothing happens and there appears to be no new files in my Downloads folder. I think it might be silently failing and that's why I am not getting any response.  Has anyone else ran into this issue?

Another thing I would like to mention is that I haven't looked through all of the documentation material about the new Profiler. I only read [this introductory blog post](https://reactjs.org/blog/2018/09/10/introducing-the-react-profiler.html), so if this issue is addressed elsewhere I apologize and also request the source to that solution.

Thank you for your time!

**Versions:**
 * `React DevTools 4.0.5`
 * `Firefox: 68.0.2(64-bit)`
 * `Ubuntu: 18.04`

}
      if (profilingData !== null) {
        const profilingDataExport = prepareProfilingDataExport(profilingData);
        const date = new Date();
        const dateString = date
          .toLocaleDateString(undefined, {
            year: 'numeric',
            month: '2-digit',
            day: '2-digit',
          })
          .replace(/\//g, '-');
        const timeString = date
          .toLocaleTimeString(undefined, {
            hour12: false,
          })
          .replace(/:/g, '-');
        downloadFile(
          `profiling-data.${dateString}.${timeString}.json`,
          JSON.stringify(profilingDataExport, null, 2),
        );
      }
    },
    [rootID, profilingData],
  );
  const uploadData = useCallback(() => {
    if (inputRef.current !== null) {
      inputRef.current.click();
    }
  }, []);
  const handleFiles = useCallback(