[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..fb98c332e5b09ff802001daabafb7ec240e9d44f 100644
--- a/components/password_manager/core/browser/password_form_manager.h
+++ b/components/password_manager/core/browser/password_form_manager.h
@@ -84,16 +84,6 @@ class PasswordFormManager : public PasswordStoreConsumer {
   // the same thread!
   bool HasCompletedMatching() const;
 
-  // Returns true if the observed form has both the current and new password
-  // fields, and the username field was not explicitly marked with
-  // autocomplete=username. In these cases it is not clear whether the username
-  // field is the right guess (often such change password forms do not contain
-  // the username at all), and the user should not be bothered with saving a
-  // potentially malformed credential. Once we handle change password forms
-  // correctly, or http://crbug.com/448351 gets implemented, this method should
-  // be replaced accordingly.
-  bool IsIgnorableChangePasswordForm() const;
-
   // Determines if the user opted to 'never remember' passwords for this form.
   bool IsBlacklisted() const;
 
@@ -130,14 +120,16 @@ class PasswordFormManager : public PasswordStoreConsumer {
   // TODO: Make this private once we switch to the new UI.
   void PermanentlyBlacklist();
 
-  // If the user has submitted observed_form_, provisionally hold on to
+  // If the user has submitted |observed_form_|, provisionally hold on to
   // the submitted credentials until we are told by PasswordManager whether
   // or not the login was successful. |action| describes how we deal with
   // possible usernames. If |action| is ALLOW_OTHER_POSSIBLE_USERNAMES we will
   // treat a possible usernames match as a sign that our original heuristics
   // were wrong and that the user selected the correct username from the
-  // Autofill UI.
-  void ProvisionallySave(const autofill::PasswordForm& credentials,
+  // Autofill UI. If the |observed_form_| is a ignorable change-password form
+  // having non-matching credentials to that of in |best_matches_|, this
+  // functions returns false; for all other cases returns true.
+  bool ProvisionallySave(const autofill::PasswordForm& credentials,
                          OtherPossibleUsernamesAction action);
 
   // Handles save-as-new or update of the form managed by this manager.
@@ -282,6 +274,16 @@ class PasswordFormManager : public PasswordStoreConsumer {
       const autofill::FormData& form_data,
       const autofill::ServerFieldType& password_type);
 
+  // Returns true if the observed form has both the current and new password
+  // fields, and the username field was not explicitly marked with
+  // autocomplete=username. In these cases it is not clear whether the username
+  // field is the right guess (often such change password forms do not contain
+  // the username at all), and the user should not be bothered with saving a
+  // potentially malformed credential. Once we handle change password forms
+  // correctly, or http://crbug.com/448351 gets implemented, this method should
+  // be replaced accordingly.
+  bool IsIgnorableChangePasswordForm() 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.