When a new user is created using GCPW the email and gaia id for the GCPW created user is added to the registry. Afterwards when the user signs in with the same email we can find the corresponding username to sign in. However if the user changes their email address this association will no longer be valid and the user will lose access to their username.
We should instead do all user associations via the gaia id which is persistent across all emails instead.
Comment 1 by rogerta@chromium.org
, Dec 12