Don't ever attempt to upload credit cards whose numbers match.

components/autofill/core/browser/credit_card.h

Index: components/autofill/core/browser/credit_card.h
diff --git a/components/autofill/core/browser/credit_card.h b/components/autofill/core/browser/credit_card.h
index 73f138c0cde376c37a2164850cc59fa453e30b07..e15c79fc20f7ee4f1108a66414e31e93c10eeddd 100644
--- a/components/autofill/core/browser/credit_card.h
+++ b/components/autofill/core/browser/credit_card.h
@@ -155,6 +155,10 @@ class CreditCard : public AutofillDataModel {
   // Determines if |this| is a local version of the server card |other|.
   bool IsLocalDuplicateOfServerCard(const CreditCard& other) const;
 
+  // Determines if |this| has the same number as |other|. If either is a masked
+  // server card, compares the last four digits only.
+  bool HasSameNumberAs(const CreditCard& other) const;
+
   // Equality operators compare GUIDs, origins, and the contents.
   // Usage metadata (use count, use date, modification date) are NOT compared.
   bool operator==(const CreditCard& credit_card) const;