Performance - Performance overlay button is confusing

It is not clear what this button is for.
When I click it, i do not see changes.
Tooltip 'Overlay a performance chart on your app' does not help to understand I need to switch focus to application, because 'on app' may mean many things.
When I click 'More info', I land to https://docs.flutter.dev/perf#the-performance-overlay, I search for word 'overlay' on the page and there is no one.

Suggestions:

- [ ] - Button name: 'Show info in app'
- [ ] - Tooltip could be 'Render performance information on top of your application'
- [ ] - Documentation should be searchable by the button label and tooltip words.