When an attacker can gain access to your unlocked computer and have time to logout/login your browser, you should not expect anything on the desktop is safe. Personally I don't see this as a security bug.
But this is not an attacker this is anyone you don't need to compile dll When you got one computer with several passwords to google accounts you can than sync them to your chrome browser and so on you can steal millions of google accounts and sync it to one malicious account. people probably doing it right now :(
Was this reported to the Chrome bug bounty program? https://www.google.com/about/appsecurity/chrome-rewards/