Add a histogram for a number of HTTP passwords migrated to HTTPS.

components/password_manager/core/browser/http_password_migrator.cc

Index: components/password_manager/core/browser/http_password_migrator.cc
diff --git a/components/password_manager/core/browser/http_password_migrator.cc b/components/password_manager/core/browser/http_password_migrator.cc
index 9f331071844c39b2e02f67eae3967f55e0725b02..8f5552ad1f24b1cd5f5bdce02aa2933553db566a 100644
--- a/components/password_manager/core/browser/http_password_migrator.cc
+++ b/components/password_manager/core/browser/http_password_migrator.cc
@@ -4,6 +4,7 @@
 
 #include "components/password_manager/core/browser/http_password_migrator.h"
 
+#include "components/password_manager/core/browser/password_manager_metrics_util.h"
 #include "components/password_manager/core/browser/password_store.h"
 #include "url/gurl.h"
 #include "url/url_constants.h"
@@ -53,6 +54,8 @@ void HttpPasswordMigrator::OnGetPasswordStoreResults(
     password_store_->AddLogin(*form);
   }
 
+  metrics_util::LogCountHttpMigratedPasswords(results.size());
+
   if (consumer_)
     consumer_->ProcessMigratedForms(std::move(results));
 }