ChangeEmailValidator: rename performValidation method

performValidation does not actually do any validation, it just matches
email address pattern to a given email. As such, rename the function to
'match' to express its actual purpose and generalize its use.

Change-Id: I5fdf5659febf81c356bcd5f6079a585cc0babb13
Signed-off-by: Matthias Maennich <maennich@google.com>
2 files changed