Well this is annoying! It used to be removed via: chrome://flags/ and then just disabling “Enable Rich Notifications Mac, Windows”, but now it is: “Notification Center behavior Mac”. You also have to leave the setting to DEFAULT, and not disabled. Then relaunch and it’s gone.
We shall see what it takes on the next go around to disable it. OY Google, please stop. Just make it the same option every time. This is current as of: Version 36.0.1985.143