A recent update of Chrome turned the previously hidden new avatar menu on by default. This avatar menu allows you to quickly change your login profile. I only ever use one profile, so the button just gets in the way, and I have a few times accidentally clicked the avatar menu instead of the minimize button (muscle memory says the minimize button is always the first button on the left, right?).
At first I wasn't sure what the name of this "avatar menu" feature was, but after a bit of digging through the chrome configuration options, I found one called "Enable the new avatar menu" that looked promising and finally removed the button. Happiness.
To hide the avatar menu button: browse to chrome://flags in your chrome browser, and search for the "
Update July 2015: This option appears to have changed to "Enable new profile management system", but there appears to be a bug which does not allow this menu to be disabled.
