If we don't fill the expiration and the user fills it himself with non-expired values, would it be interesting to overwrite the old dates?

Yes. I actually had that in the original description and then deleted it. I was thinking perhaps it deserved its own bug. But I would be supportive of this bug also including the logic to update cards when the card # and name on card is the same but the expiration differs on form submit.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3cf9514720966c9b1cd77c7376c6670342ae97bf

commit 3cf9514720966c9b1cd77c7376c6670342ae97bf
Author: sebsg <sebsg@chromium.org>
Date: Wed Apr 13 21:02:53 2016

Do not fill the expiration date of expired credit cards in Autofill.

Moved the GenerateSelectFieldWithOptions method from autofill_field_unittest.cc to CreateTestSelectField in autofill_test_util.cc

BUG= 602429 

Review URL: https://codereview.chromium.org/1885773002

Cr-Commit-Position: refs/heads/master@{#387082}

[modify] https://crrev.com/3cf9514720966c9b1cd77c7376c6670342ae97bf/components/autofill/core/browser/autofill_field_unittest.cc
[modify] https://crrev.com/3cf9514720966c9b1cd77c7376c6670342ae97bf/components/autofill/core/browser/autofill_manager.cc
[modify] https://crrev.com/3cf9514720966c9b1cd77c7376c6670342ae97bf/components/autofill/core/browser/autofill_manager_unittest.cc
[modify] https://crrev.com/3cf9514720966c9b1cd77c7376c6670342ae97bf/components/autofill/core/browser/autofill_test_utils.cc
[modify] https://crrev.com/3cf9514720966c9b1cd77c7376c6670342ae97bf/components/autofill/core/browser/autofill_test_utils.h
[modify] https://crrev.com/3cf9514720966c9b1cd77c7376c6670342ae97bf/components/autofill/core/browser/credit_card.cc
[modify] https://crrev.com/3cf9514720966c9b1cd77c7376c6670342ae97bf/components/autofill/core/browser/credit_card.h
[modify] https://crrev.com/3cf9514720966c9b1cd77c7376c6670342ae97bf/components/autofill/core/browser/personal_data_manager.cc