Google already has a multiple-sign feature  that allows users to sign into multiple Google accounts at the same time. Google is now rolling out something called the ‘Account Chooser’ which makes it easier for people that regularly log into multiple different Google accounts.
You know how browsers can save the username/e-mail and/or password of a login, so you don’t have to type it in again the next time you visit a website? Yeah, well, Account Chooser is pretty much the same thing except it is for Google accounts (Gmail, Google+, etc.). What Account Chooser does is it lists all the Google accounts you have logged into previously:
From that list you simply click on the account you want to login and Google brings up that account:
If you have your browser set to save passwords, then the password field will be prepopulated for you. If you don’t have your browser set to save passwords, then only the username/e-mail field will be prepopulated.
If you don’t like the idea of Account Chooser, don’t worry. As of right now you must manually enable Account Chooser  to use it; however, it may be automatically enabled for all accounts in the future in which case you can opt-out  if you don’t want it. Also, if you decide to use Account Chooser, you don’t have to use it with all of your Google accounts — you can pick and choose. Before an account is shown in the Account Chooser list, you must manually give permission for an account to be used with Account Chooser:
As you can see from the above screenshot, you can either give permission or not give permission.
If you ever want to remove an account from the Account Chooser list, you can simply clear your browser cookies or click the “Edit” button and manually remove an account from the list:
For those wondering how Account Chooser is different from multiple sign-in, get this: Account Chooser does not replace multiple sign-in but rather supplements it. Account Chooser works wherever Google account signs are; this includes when logging in for multiple sign-in. In other words, when you go to log into another account using multiple sign-in, Account Chooser is there listing all your recently used accounts.
Personally speaking, I will not be using Account Chooser because it just adds another click for me before I can use Roboform to sign in. However, for those of us that don’t use password managers, Account Chooser can be very useful if we regularly use more than one Google account. Just be sure to use it wisely if you are on a shared computer.