Repro
(1) Have a visa 4111...1111
(2) Go in Payment Request and the flow to add a credit card
(3) Add the same 4111....1111 card
Now you have two copies!
Before adding a new card from the Payment Request UI, we should first check if it doesn't already exist.
Assigning to MAD because he's been looking at this code.
Comment 1 by mad@chromium.org
, May 15 2017