How can you tell if someone is online in hangouts?

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Tags

1. #their
2. #google
3. #indicators
4. #online
5. #friend
6. #green
7. #people
8. #active
9. #hangouts
10. #offline
11. #indicator
12. #users
13. #using
14. #status
15. #plugin
16. #chrome
17. #windows