Password generation on password change forms has a pretty bad user experience:

In the following we assume that you have a password stored for a site on which you want to generate a new password. This is a pair of (username, password).

Steps: 
1. You go to the password change form and generate a password.
2. Chrome stores the generated password with an empty username.
3. You submit the form and get a confirmation that the credential was saved.
4. Now you have two credentials: the old (username, password) and the new (empty, password).