Currently, we have two Credit Card editors in Chrome for Android:

(1) Settings -> Autofill forms -> Edit or Add a credit card
(2) Payment Request UI -> Edit or Add a credit card (a good test site for this is https://rsolomakhin.github.io/)

The code location for (1) is https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/preferences/autofill/?q=AutofillEditor&sq=package:chromium&dr=CSs

The code location for (2) is https://cs.chromium.org/chromium/src/chrome/android/java/src/org/chromium/chrome/browser/payments/CardEditor.java?dr=CSs&q=CardEditor&sq=package:chromium&l=45

Both editors have slightly different code structures, but the fact remains that they should be the same editor, especially since there are mocks to improve the flow to "Add a credit card".