Enable manual password autofilling if the username field is read-only.

components/autofill/content/renderer/password_autofill_agent.cc

Index: components/autofill/content/renderer/password_autofill_agent.cc
diff --git a/components/autofill/content/renderer/password_autofill_agent.cc b/components/autofill/content/renderer/password_autofill_agent.cc
index 34e28598f3145eb9c75ac0ff73b0ef58e46d428d..d15bcb71f88e1cb2c057606ba9d7ffa5fb88d7ae 100644
--- a/components/autofill/content/renderer/password_autofill_agent.cc
+++ b/components/autofill/content/renderer/password_autofill_agent.cc
@@ -703,8 +703,6 @@ bool PasswordAutofillAgent::FillSuggestion(
 
   if (!FindPasswordInfoForElement(*element, &username_element,
                                   &password_element, &password_info) ||
-      (!username_element.isNull() &&
-       !IsElementAutocompletable(username_element)) ||
       !IsElementAutocompletable(password_element)) {
     return false;
   }
@@ -749,8 +747,6 @@ bool PasswordAutofillAgent::PreviewSuggestion(
 
   if (!FindPasswordInfoForElement(*element, &username_element,
                                   &password_element, &password_info) ||
-      (!username_element.isNull() &&
-       !IsElementAutocompletable(username_element)) ||
       !IsElementAutocompletable(password_element)) {
     return false;
   }