I'll try and explain this the best I can. My friend was over and needed to use my computer so I opened a new person profile for them to use. They logged into their gmail google account which also was shown on the side of googles home page that their account was logged in. They forgot to log out when finished and I thought I was signed out of my chrome profile on the top right of the web page so I logged into my profile and linked my account to the new guest page. I realized that they were logged into their google account after. Since we were both logged in on the same browser will all my past history and passwords be linked to his google account now? Since he was logged into the gmail and google/YouTube account when I logged into the chrome profile. I know my current web activity would be synced to his google account since he was signed in. I mean will all previous activity and passwords before I logged into the same browser be present to him. Sorry about the long post, just trying my best to explain.