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`

const blob = new Blob([text], {type: 'text/plain;charset=utf-8'});
  if (downloadUrl !== null) {
    URL.revokeObjectURL(downloadUrl);
  }
  downloadUrl = URL.createObjectURL(blob);
  const element = document.createElement('a');
  element.setAttribute('href', downloadUrl);
  element.setAttribute('download', filename);
  element.style.display = 'none';
  ((document.body: any): HTMLBodyElement).appendChild(element);
  element.click();
  ((document.body: any): HTMLBodyElement).removeChild(element);
}
export function truncateText(text: string, maxLength: number): string {
  const {length} = text;
  if (length > maxLength) {
    return (
      text.substr(0, Math.floor(maxLength / 2)) +
      '…' +
      text.substr(length - Math.ceil(maxLength / 2) - 1)
    );
  } else {
    return text;
  }
}