Report the number of empty usernames without a nonempty pair.

components/password_manager/core/browser/login_database_unittest.cc

Index: components/password_manager/core/browser/login_database_unittest.cc
diff --git a/components/password_manager/core/browser/login_database_unittest.cc b/components/password_manager/core/browser/login_database_unittest.cc
index c45cc5f40aed23079159ebddbf9f3d7ec990ad61..a82b2c765a9c20d8f273db6e095c339ea2fee6a6 100644
--- a/components/password_manager/core/browser/login_database_unittest.cc
+++ b/components/password_manager/core/browser/login_database_unittest.cc
@@ -1055,12 +1055,22 @@ TEST_F(LoginDatabaseTest, ReportMetricsTest) {
   password_form.blacklisted_by_user = true;
   EXPECT_EQ(AddChangeForForm(password_form), db().AddLogin(password_form));
 
+  password_form.origin = GURL("http://sixth.example.com/");
+  password_form.signon_realm = "http://sixth.example.com/";
+  password_form.username_value = ASCIIToUTF16("");
+  password_form.password_value = ASCIIToUTF16("my_password");
+  password_form.blacklisted_by_user = false;
+  EXPECT_EQ(AddChangeForForm(password_form), db().AddLogin(password_form));

[engedy, 2015/04/15 15:29:26]

Just to be on the safe side, could you please add another one with an empty
username for this domain? To make it clear how/that multiplicities are correctly
handled.

[msramek, 2015/04/16 14:34:26]

Since CountInDatabase counts +1 for every entry, without looking for
duplicities, so should NotPairedWithNonempty.

However, note that since for this domain there *exists* a nonempty username
entry, adding another empty username entry won't change the count (which is 1,
coming from fourth.example.com.

[engedy, 2015/04/16 14:44:32]

Yeah, I wanted to add this comment to "fourth", but on second thought it does
not make much sense. However, if you go with the negated solution as suggested
by Vasilii, please add another nonempty username for "sixth" to make sure the
one empty still only counts as one. (This is mostly blackbox testing. It would
be needed for a JOIN-based solution.)

+
+  password_form.username_value = ASCIIToUTF16("my_username");
+  EXPECT_EQ(AddChangeForForm(password_form), db().AddLogin(password_form));
+
   base::HistogramTester histogram_tester;
   db().ReportMetrics("", false);
 
   histogram_tester.ExpectUniqueSample(
       "PasswordManager.TotalAccounts.UserCreated.WithoutCustomPassphrase",
-      4,
+      6,
       1);
   histogram_tester.ExpectBucketCount(
       "PasswordManager.AccountsPerSite.UserCreated.WithoutCustomPassphrase",
@@ -1069,7 +1079,7 @@ TEST_F(LoginDatabaseTest, ReportMetricsTest) {
   histogram_tester.ExpectBucketCount(
       "PasswordManager.AccountsPerSite.UserCreated.WithoutCustomPassphrase",
       2,
-      1);
+      2);
   histogram_tester.ExpectBucketCount(
       "PasswordManager.TimesPasswordUsed.UserCreated.WithoutCustomPassphrase",
       0,
@@ -1100,6 +1110,10 @@ TEST_F(LoginDatabaseTest, ReportMetricsTest) {
       1);
   histogram_tester.ExpectUniqueSample(
       "PasswordManager.EmptyUsernames.CountInDatabase",
+      2,
+      1);
+  histogram_tester.ExpectUniqueSample(
+      "PasswordManager.EmptyUsernames.NotPairedWithNonempty",
       1,
       1);
 }