[Payments] Changes to validation in the Credit Card editor
Several changes are bundled here:
* Card icons will now dim dynamically as the network is selected.
* ValidatingTextfield::IsValid no longer has side effects
* Error labels are refreshed differently
* ValidationDelegate now gets passed |was_blurred| for textfield, to
allow performing some tasks before the blur (selecting card icons).
* Reverse the validity logic on the expiration custom view (oops).
BUG=
721619
TEST=existing
Review-Url:
https://codereview.chromium.org/2896263002
Cr-Commit-Position: refs/heads/master@{#474060}
Committed:
https://chromium.googlesource.com/chromium/src/+/dbe9253353485376a03c2c35bdd462922ecb80af