Messages should disappear when connection state changes.

[polina-c]

Steps to repro:

1. Run DevTools with experiments
2. Connect to an app in debug mode
3. Open memory screen
4. See popup message
5. Do not close the message
6. Switch to tab 'Flutter DevTools'
7. Disconnect from an app
8. Open memory screen again
9. Actual: find message is still here; expected: the message should disappear because state changed

[polina-c]

@kenzieschmoll

What do you think is right place to fix this?