Edit button makes username editable in the password manager bubble.

chrome/browser/ui/views/passwords/manage_password_items_view.h

Index: chrome/browser/ui/views/passwords/manage_password_items_view.h
diff --git a/chrome/browser/ui/views/passwords/manage_password_items_view.h b/chrome/browser/ui/views/passwords/manage_password_items_view.h
index 66c5819a23123e1c83c2370d635f8417f1f1323a..94235dac4e3cd90085d7ed615d804b6334bd73dc 100644
--- a/chrome/browser/ui/views/passwords/manage_password_items_view.h
+++ b/chrome/browser/ui/views/passwords/manage_password_items_view.h
@@ -10,10 +10,20 @@
 
 #include "base/macros.h"
 #include "components/autofill/core/common/password_form.h"
+#include "ui/views/controls/label.h"
+#include "ui/views/controls/textfield/textfield.h"
 #include "ui/views/view.h"
 
 class ManagePasswordsBubbleModel;
 
+// Standalone functions for creating username and password views.
+std::unique_ptr<views::Label> GenerateUsernameLabel(
+    const autofill::PasswordForm& form);
+std::unique_ptr<views::Label> GeneratePasswordLabel(
+    const autofill::PasswordForm& form);
+std::unique_ptr<views::Textfield> GenerateUsernameEditable(
+    const autofill::PasswordForm& form);
+
 // A custom view of individual credentials. The view is represented as a table
 // where each row can be in three distinct states:
 //