[Autofill] Fixed logging of network matches and mismatches.

Logging will now only occur when one of the two cards being compared is
a masked card and the two cards' last four digits match.

Previously, logging was occuring regardless of whether or not the last
four digits matched.

Change-Id: I1a0d9d44df52cf9b6853dbaab041d05a1585e230
Reviewed-on: https://chromium-review.googlesource.com/c/1486431Reviewed-by: Tommy Martino <tmartino@chromium.org>
Reviewed-by: Fabio Tirelo <ftirelo@chromium.org>
Commit-Queue: Caitlin Fischer <caitlinfischer@google.com>
Cr-Commit-Position: refs/heads/master@{#635766}

components/autofill/core/browser/credit_card.cc

@@ -661,12 +661,16 @@ bool CreditCard::HasSameNumberAs(const CreditCard& other) const {
   // cards matches.
   if (record_type() == MASKED_SERVER_CARD ||
       other.record_type() == MASKED_SERVER_CARD) {
+    bool last_four_digits_match = LastFourDigits() == other.LastFourDigits();
     // The below metric is logged because this function previously compared
     // cards' last four digits and networks if one card was masked. It may be
-    // useful to know how often networks match; however, it is expected that the
-    // number of discrepanies will be low.
+    // useful to know how often networks match when the last four digits match.
+    // It is expected that when two cards' last four digits are the same, their
+    // networks will almost always match, too.
+    if (last_four_digits_match) {
       AutofillMetrics::LogMaskedCardComparisonNetworksMatch(
           NetworkForDisplay() == other.NetworkForDisplay());
+    }
 
     bool months_match = expiration_month() == other.expiration_month() ||
                         expiration_month() == 0 ||
@@ -675,8 +679,7 @@ bool CreditCard::HasSameNumberAs(const CreditCard& other) const {
     bool years_match = expiration_year() == other.expiration_year() ||
                        expiration_year() == 0 || other.expiration_year() == 0;
 
-    return LastFourDigits() == other.LastFourDigits() && months_match &&
-           years_match;
+    return last_four_digits_match && months_match && years_match;
   }
 
   return StripSeparators(number_) == StripSeparators(other.number_);

components/autofill/core/browser/credit_card_unittest.cc

@@ -624,12 +624,13 @@ TEST(CreditCardTest, HasSameNumberAs_LogMaskedCardComparisonNetworksMatch) {
   CreditCard b(base::GenerateGUID(), std::string());
 
   a.set_record_type(CreditCard::MASKED_SERVER_CARD);
+  a.SetRawInfo(CREDIT_CARD_NUMBER, ASCIIToUTF16("4111111111111111"));
   a.SetNetworkForMaskedCard(kVisaCard);
   // CreditCard b's network is set to kVisaCard because it starts with 4, so the
   // two cards have the same network.
   b.SetRawInfo(CREDIT_CARD_NUMBER, ASCIIToUTF16("4111111111111111"));
   base::HistogramTester histogram_tester;
-  EXPECT_FALSE(a.HasSameNumberAs(b));
+  EXPECT_TRUE(a.HasSameNumberAs(b));
   histogram_tester.ExpectUniqueSample(
       "Autofill.MaskedCardComparisonNetworksMatch", true, 1);
 }
@@ -640,11 +641,14 @@ TEST(CreditCardTest,
   CreditCard b(base::GenerateGUID(), std::string());
 
   a.set_record_type(CreditCard::MASKED_SERVER_CARD);
+  a.SetRawInfo(CREDIT_CARD_NUMBER, ASCIIToUTF16("4111111111111111"));
   a.SetNetworkForMaskedCard(kDiscoverCard);
-  // CreditCard b's network is set to kVisaCard because it starts with 4.
+  // CreditCard b's network is set to kVisaCard because it starts with 4. The
+  // two cards have the same last four digits, but their networks are different,
+  // so this discrepancy should be logged.
   b.SetRawInfo(CREDIT_CARD_NUMBER, ASCIIToUTF16("4111111111111111"));
   base::HistogramTester histogram_tester;
-  EXPECT_FALSE(a.HasSameNumberAs(b));
+  EXPECT_TRUE(a.HasSameNumberAs(b));
   histogram_tester.ExpectUniqueSample(
       "Autofill.MaskedCardComparisonNetworksMatch", false, 1);
 }