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`

case 'typed_array':
      return `${name}[${data[meta.size]}]`;
    default:
      return null;
  }
}
function sanitize(data: Object): void {
  for (const key in data) {
    const value = data[key];
    if (value && value[meta.type]) {
      data[key] = getMetaValueLabel(value);
    } else if (value != null) {
      if (Array.isArray(value)) {
        sanitize(value);
      } else if (typeof value === 'object') {
        sanitize(value);
      }
    }
  }
}
export function serializeDataForCopy(props: Object): string {
  const cloned = Object.assign({}, props);
  sanitize(cloned);
  try {
    return JSON.stringify(cloned, null, 2);
  } catch (error) {
    return '';
  }
}
export function serializeHooksForCopy(hooks: HooksTree | null): string {