[Password Manager] Modified to support saving passwords on forms without username fields.

components/autofill/core/common/password_form_fill_data.cc

Index: components/autofill/core/common/password_form_fill_data.cc
diff --git a/components/autofill/core/common/password_form_fill_data.cc b/components/autofill/core/common/password_form_fill_data.cc
index 7dbc97d0ab62b42dc7b158bcea47b663d7fcd149..1902bda66c652cdbb534ba60d6c53be43d87c460 100644
--- a/components/autofill/core/common/password_form_fill_data.cc
+++ b/components/autofill/core/common/password_form_fill_data.cc
@@ -39,21 +39,23 @@ void InitPasswordFormFillData(
   // Note that many of the |FormFieldData| members are not initialized for
   // |username_field| and |password_field| because they are currently not used
   // by the password autocomplete code.
-  FormFieldData username_field;
-  username_field.name = form_on_page.username_element;
-  username_field.value = preferred_match->username_value;
+  if (!form_on_page.username_element.empty()) {
+    FormFieldData username_field;
+    username_field.name = form_on_page.username_element;
+    username_field.value = preferred_match->username_value;
+    result->basic_data.fields.push_back(username_field);
+  }
+
   FormFieldData password_field;
   password_field.name = form_on_page.password_element;
   password_field.value = preferred_match->password_value;
   password_field.form_control_type = "password";
+  result->basic_data.fields.push_back(password_field);
 
   // Fill basic form data.
   result->basic_data.origin = form_on_page.origin;
   result->basic_data.action = form_on_page.action;
-  result->basic_data.fields.push_back(username_field);
-  result->basic_data.fields.push_back(password_field);
   result->wait_for_username = wait_for_username_before_autofill;
-
   result->preferred_realm = preferred_match->original_signon_realm;
 
   // Copy additional username/value pairs.