I think the whole point is now that you go to the chat page if you want to chat and the game page if you want to play. (Hence why there is no change room dialogue in the game page).

nonoba made a chat yay

Seriously, I don't see a good reason to reduce the size of the previous chat box. Most of the space is being flat-out wasted with the name and icon for the game. The number of plays and overall rating don't really warrant that prominent position of screen real estate either. All of that information could be comfortably moved to the 'About the game' tab. That'd only leave the new tab bar with "Top Games" and "Chat".