![](https://media.giphy.com/media/l0ExdBwqD6YkeEhQ4/giphy-downsized.gif)

Fixes https://github.com/flutter/devtools/issues/5946

While preparing DevTools for the Multi View changes, I noticed that
inspecting a Tooltip causes an stack overflow.
This PR addresses that issue by fixing the scope of the subtreeDepth variable and adding some other idiomatic fixes