What is CryptoTokenExtension in Chromium extensions?

It is the extension that allows two-step verification between hardware. From the link:

Multi-factor authentication (MFA) is a method of computer access control in which a user is only granted access after successfully presenting several separate pieces of evidence to an authentication mechanism – typically at least two of the following categories: knowledge (something they know), possession (something they have), and inherence (something they are).

Two-factor authentication (also known as 2FA) is a method of confirming a user's claimed identity by utilizing a combination of two different components. Two-factor authentication is a type of multi-factor authentication.

It is supported by Google Chrome since version 38 and Opera since version 40. Firefox has an add-on for this. And Microsoft has plans to implement it. Dropbox, GitHub, GitLab and Bitbucket support it too.

Is it safe to use?

Well... the tool itself is there to protect you from misuse. But it all depends on how you treat your hardware I would say. On the other hands... it IS a tracking tool so Richard Stallman will disagree (strongly and furiously) (:))