Add UMA histograms for tracking empty usernames.

components/password_manager/core/browser/login_database.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/password_manager/core/browser/login_database.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/bind.h"
@@ skipping 436 matching lines @@
       std::string username = sync_statement.ColumnString(0);
       if (gaia::AreEmailsSame(sync_username, username)) {
         syncing_account_saved = true;
         break;
       }
     }
   }
   UMA_HISTOGRAM_ENUMERATION("PasswordManager.SyncingAccountState",
                             2 * sync_username.empty() + syncing_account_saved,
                             4);
+
+  sql::Statement empty_usernames_statement(db_.GetCachedStatement(
+      SQL_FROM_HERE, "SELECT COUNT(*) FROM logins "
+                     "WHERE blacklisted_by_user=0 AND username_value=''"));
+  if (empty_usernames_statement.Step()) {
+    int empty_forms = empty_usernames_statement.ColumnInt(0);
+    UMA_HISTOGRAM_COUNTS_100("PasswordManager.EmptyUsernames.CountInDatabase",
+                             empty_forms);
+  }
 }
 
 PasswordStoreChangeList LoginDatabase::AddLogin(const PasswordForm& form) {
   PasswordStoreChangeList list;
   if (!DoesMatchConstraints(form))
     return list;
   std::string encrypted_password;
   if (EncryptedString(form.password_value, &encrypted_password) !=
       ENCRYPTION_RESULT_SUCCESS)
     return list;
@@ skipping 413 matching lines @@
 
 bool LoginDatabase::DeleteAndRecreateDatabaseFile() {
   DCHECK(db_.is_open());
   meta_table_.Reset();
   db_.Close();
   sql::Connection::Delete(db_path_);
   return Init();
 }
 
 }  // namespace password_manager