[Smart Lock, Prefs reconciliation] Prefs migration logic for desktop platforms.

chrome/browser/password_manager/password_manager_setting_migrater_service.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_MANAGER_SETTING_MIGRATER_SERVICE_H_
+#define CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_MANAGER_SETTING_MIGRATER_SERVICE_H_
+
+#include <vector>
+
+#include "base/memory/singleton.h"
+#include "base/prefs/pref_change_registrar.h"
+#include "chrome/browser/prefs/pref_service_syncable_observer.h"
+#include "components/keyed_service/content/browser_context_keyed_service_factory.h"
+#include "components/keyed_service/core/keyed_service.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class Profile;
+
+namespace sync_driver {
+class SyncService;
+}
+
+// PasswordManagerSettingMigraterService is responsible for reconciling Chrome

[engedy, 2015/08/31 18:17:23]

Phrasing nit:

Given the complexity and the vast number of edge cases, we should give a summary
of them in this comment. It could go like this:

// Service that is responsible for reconciling the legacy "Offer to save your
// web passwords" setting with the new "Enable Smart Lock for Passwords"
// setting. 
//
// It works as follows:
//
//    [...]

[melandory, 2015/09/02 13:15:39]

Done.

+// password manager and Smart Lock for passwords settings.
+// Note: componetization of this service currently is impossible, because it
+// depends on PrefServiceSyncable.
+class PasswordManagerSettingMigraterService
+    : public KeyedService,
+      public PrefServiceSyncableObserver,
+      public content::NotificationObserver {
+ public:
+  class Factory : public BrowserContextKeyedServiceFactory {
+   public:
+    static Factory* GetInstance();
+    static PasswordManagerSettingMigraterService* GetForProfile(
+        Profile* profile);
+
+   private:
+    friend struct DefaultSingletonTraits<Factory>;
+    friend class PasswordManagerSettingMigraterServiceTest;
+
+    Factory();
+    ~Factory() override;
+
+    // BrowserContextKeyedServiceFactory

[engedy, 2015/08/31 18:17:23]

nit: Add colon (:) at the end. Same below, 3 places altogether.

[melandory, 2015/09/02 13:15:39]

Done.

+    KeyedService* BuildServiceInstanceFor(
+        content::BrowserContext* profile) const override;
+    bool ServiceIsCreatedWithBrowserContext() const override;
+  };
+
+  explicit PasswordManagerSettingMigraterService(Profile* profile);
+  ~PasswordManagerSettingMigraterService() override;
+
+  void Shutdown() override;
+
+  // PrefServiceSyncableObserver
+  void OnIsSyncingChanged() override;
+
+  // content::NotificationObserver
+  void Observe(int type,
+               const content::NotificationSource& source,
+               const content::NotificationDetails& details) override;
+
+ private:
+  // Initializes the observers: preferences observers and sync status observers.
+  void InitObservers();
+
+  // Called on event of changing kCredentialsEnableService preference. Changes

[engedy, 2015/08/31 18:17:23]

Phrasing nit: What do you think about simply saying:

// Called when the value of the |kCredentialsEnableService| preference changes,
and updates the value of |kPasswordManagerSavingEnabled| accordingly.

[melandory, 2015/09/02 13:15:39]

Done.

+  // the value of kPasswordManagerSavingEnabled preference to be in sync with
+  // kCredentialsEnableService.
+  void OnCredentialsEnableServicePrefChanged(
+      const std::string& changed_pref_name);
+
+  // Called on event of changing kPasswordManagerSavingEnabled preference.
+  // Changes the value of kCredentialsEnableService preference to be in sync
+  // with kPasswordManagerSavingEnabled.
+  void OnPasswordManagerSavingEnabledPrefChanged(
+      const std::string& changed_pref_name);
+
+  // Turns off one pref if another pref is off.
+  void MigrateOffState(PrefService* prefs);
+
+  // Performs a migration after sync associates models. Migration is performed
+  // based on initial values for both preferences and values received from
+  // sync.
+  void MigrateAfterModelAssociation(PrefService* prefs);
+
+  Profile* const profile_;
+  sync_driver::SyncService* sync_service_;
+  PrefChangeRegistrar pref_change_registrar_;
+
+  // Used to register for notification that profile creation is complete.
+  content::NotificationRegistrar registrar_;
+
+  // This vector contains initial value for both preferences. The vector maximum
+  // size is two, where first element is new kCredentialsEnableService
+  // preference
+  // and second element is legacy kPasswordManagerSavingEnabled preference.
+  std::vector<bool> initial_values_;
+
+  // Contains values which has came from sync during model association step.
+  // After both preferences data types are associated, new value for the both
+  // preferences will be calculated.
+  std::vector<bool> sync_data_;
+
+  DISALLOW_COPY_AND_ASSIGN(PasswordManagerSettingMigraterService);
+};
+
+#endif  // CHROME_BROWSER_PASSWORD_MANAGER_PASSWORD_MANAGER_SETTING_MIGRATER_SERVICE_H_