[PasswordManager] Improve detection of ignorable change password forms.

components/password_manager/core/browser/password_form_manager.h

Index: components/password_manager/core/browser/password_form_manager.h
diff --git a/components/password_manager/core/browser/password_form_manager.h b/components/password_manager/core/browser/password_form_manager.h
index efda7d3cf91490ceb1242a884e301d2c7b13310e..494e934b34d4cb29361e681e48cf5ee19c40f0a2 100644
--- a/components/password_manager/core/browser/password_form_manager.h
+++ b/components/password_manager/core/browser/password_form_manager.h
@@ -282,6 +282,14 @@ class PasswordFormManager : public PasswordStoreConsumer {
       const autofill::FormData& form_data,
       const autofill::ServerFieldType& password_type);
 
+  // Returns true if |candidate|'s registry controlled domain for origin and
+  // password matches with one of the stored password form within
+  // |best_matches_|; otherwise false. On success, |matching_form| holds the
+  // matching password form.
+  bool HasMatchingCredentialsInStore(
+      const autofill::PasswordForm& candidate,
+      autofill::PasswordForm* matching_form) const;
+
   // Set of PasswordForms from the DB that best match the form
   // being managed by this. Use a map instead of vector, because we most
   // frequently require lookups by username value in IsNewLogin.