Refresh for timeline events causes error.

[polina-c]

(Why error reporting is for googlers only? ) Reported bug: b/330902003

It is not 100% reproducible.

Rough steps:

1. Run devtools on chrome in profile mode
2. Connect to counter on mac
3. Turn CPU samples on/off/on and click some frames
4. Refresh the table
5. Get error
6. Switch to memory screen and get memory snapshot
7. Try to export it (you will get error)
8. Switch back to CPU > timeline to see error again
9. Let the error be here for 5 min and may be you will get crash

[polina-c]

[elliette]

FYI @kenzieschmoll