[Password Autofill] Make better use of prefilled usernames.

components/autofill/content/renderer/password_autofill_agent.h

Index: components/autofill/content/renderer/password_autofill_agent.h
diff --git a/components/autofill/content/renderer/password_autofill_agent.h b/components/autofill/content/renderer/password_autofill_agent.h
index a389ed2fae6e892fa67b794943690132c647bdaf..4a177193db78f4cd91cd8cfc15c460d045cd3977 100644
--- a/components/autofill/content/renderer/password_autofill_agent.h
+++ b/components/autofill/content/renderer/password_autofill_agent.h
@@ -107,6 +107,15 @@ class PasswordAutofillAgent : public content::RenderViewObserver {
   bool ShowSuggestionPopup(const PasswordFormFillData& fill_data,
                            const WebKit::WebInputElement& user_input);
 
+  // When passwords are first recieved, see if it can be used to autofill. This
+  // will try to autofill with the preferred username, but if the username
+  // field has a prefilled value it will try to fill the password for that
+  // username instead.
+  void FillFormOnPasswordRecieved(const PasswordFormFillData& fill_data,
+                                  const WebKit::WebFormElement& form_element,
+                                  WebKit::WebInputElement username_element,
+                                  WebKit::WebInputElement password_element);
+
   bool FillUserNameAndPassword(
       WebKit::WebInputElement* username_element,
       WebKit::WebInputElement* password_element,