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`

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