The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ffd476b19f33472d40f4c48905561b28f1ca7ab6

commit ffd476b19f33472d40f4c48905561b28f1ca7ab6
Author: Rouslan Solomakhin <rouslan@chromium.org>
Date: Wed May 24 12:46:01 2017

Format-as-you-type the card number in desktop web payment UI.

Before this patch, editing a credit card with number "4111111111111111"
or typing that number manually into the card editor would leave the
number as-is. The long string of digits hard to read.

This patch adds a formatter to the card number field that inserts two
spaces into the number for American Express cards and three spaces for
all other cards when initially opening the editor and while the user is
typing. The number is always saved without any separators.

After this patch, editing a credit card with number "4111111111111111"
will start the editor with pre-formatted number "4111 1111 1111 1111".
The card number is also formatted as the user types. The formatted
number easier to read.

Bug:  725634 
Change-Id: I26a974d302731374f1acb1d81e195855f410e6b3
Reviewed-on: https://chromium-review.googlesource.com/513542
Reviewed-by: Anthony Vallee-Dubois <anthonyvd@chromium.org>
Commit-Queue: Anthony Vallee-Dubois <anthonyvd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#474264}
[modify] https://crrev.com/ffd476b19f33472d40f4c48905561b28f1ca7ab6/chrome/browser/ui/views/payments/credit_card_editor_view_controller.cc
[modify] https://crrev.com/ffd476b19f33472d40f4c48905561b28f1ca7ab6/chrome/browser/ui/views/payments/credit_card_editor_view_controller.h
[modify] https://crrev.com/ffd476b19f33472d40f4c48905561b28f1ca7ab6/chrome/browser/ui/views/payments/credit_card_editor_view_controller_browsertest.cc